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Guide to the 2023 Review of Parliamentary constituencies

Developing proposals – requirements and policy

Statutory electorate range

  1. The Act sets out a number of Rules in Schedule 2 which are relevant to the detailed development of proposals for individual constituencies. Foremost among these is Rule 2, which provides that – apart from five specified exceptions – every constituency we recommend must have an electorate (as at 2 March 2020) that is no less than 95% and no more than 105% of the ‘UK electoral quota’. The UK electoral quota for the 2023 Review is, to the nearest whole number, 73,393.
  2. Accordingly, every recommended constituency (except the five ‘protected’ constituencies) must have an electorate as at 2 March 2020 that is no smaller than 69,724 and no larger than 77,062.
  3. The specified exceptions to this in England are the two constituencies for the Isle of Wight. However, in all other aspects of the 2023 Review, the Isle of Wight is treated in the same way as other parts of England.
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Other statutory factors

  1. Rule 5 in Schedule 2 provides for a number of other factors that the BCE may take into account in establishing a new map of constituencies for the 2023 Review, specifically:
  • special geographical considerations, including in particular the size, shape and accessibility of a constituency;
  • local government boundaries as they existed (or were in prospect) on 1 December 2020 (see paragraph 16 above);
  • boundaries of existing constituencies;
  • any local ties that would be broken by changes in constituencies; and
  • the inconveniences attendant on such changes.

Special geographical considerations

  1. The BCE considers that special geographical considerations that may have an impact on the ability to form a constituency with an electorate within the statutory electorate range will primarily relate to physical geography such as mountains, hills, lakes, rivers, estuaries, islands, and major roads, rather than to human or social geography. Matters of culture, history, socio-economics and other possible aspects of non-physical geography are more likely to arise as issues when considering the separate factor of ‘local ties’.

Local government boundaries and local ties

  1. The BCE may take into account local government boundaries. These include both the external boundaries of local councils and their internal – ward or electoral division – boundaries.
  2. While the BCE proposes to identify constituencies by reference to local authority external boundaries as far as practicable, it is nevertheless often necessary to cross these boundaries in order to form constituencies that comply with the statutory electorate range.
  3. The BCE uses wards (in district and borough council areas) or electoral divisions (in areas of unitary authorities that have a county status) as the basic building block for designing constituencies. The use of the term ‘ward’ throughout the rest of this document should be taken to include electoral divisions in unitary authorities.
  4. Wards are well-defined and well-understood units, which are generally indicative of areas which have a broad community of interest. Any division of a ward between constituencies would therefore risk breaking local ties, as well as adding complexity to both the task of Returning Officers in administering a Parliamentary election in the area, and the ‘grass roots’ co-ordination of political party activism. The BCE’s view is therefore that wards should continue to be the default building block for constituencies. However, the BCE recognises that there may be circumstances where the splitting of a ward may be necessary to achieve a scheme of constituencies locally that better meets the ‘Rule 5’ statutory criteria overall (see paragraph 26 above). In limited circumstances, we would therefore consider the splitting of a ward between constituencies. Those circumstances are:
  • Where splitting a ward would significantly enhance the ability of the BCE to adhere to existing or prospective local authority boundaries (i.e. avoid constituencies crossing local authorities), maintain existing constituencies unchanged, and/or preserve local ties, without causing consequential significant problems for surrounding constituencies.
  • Where the division of a ward would avoid the alternative of a significant ‘domino effect’ of change to a wide area if wards were to be kept whole. This is likely to be an issue in metropolitan areas, where wards often have large electorates: an example from a previous Review was the BCE’s recommendation to split three wards in the West Midlands metropolitan area, which minimised the need to cross local council boundaries, and prevented an otherwise radical ‘domino effect’ of change across the whole metropolitan area and beyond.
  • Where the division of a ward would avoid otherwise unacceptable outcomes forced by local geographical factors: an example from a previous Review was the BCE’s acceptance of the need to split a rural ward near Tewkesbury to avoid a proposed Forest of Dean constituency otherwise having to take in an urban area of Gloucester.
  1. Additionally, where the splitting of wards is proposed, BCE would wish to adhere to the following policies:
  • The number of such ward splits should be the smallest number possible, commensurate with achieving the objectives set out in paragraph 31 above.
  • The split of a ward should generally be done on the basis of the boundaries of the component polling districts that form part of that ward, as polling districts are an existing recognised unit of electoral administration (but see paragraph 40 below).
  • Wherever possible, the splitting of a ward should be done such that the separated parts of the ward will nonetheless remain in constituencies where the returning officer for each of the constituencies is likely to be the same individual (i.e. ward splits should where possible be contained within a single local authority area): this is consistent with our policy in relation to ‘orphan wards’ below.

Boundaries of existing constituencies

  1. The BCE intends to have regard generally to existing constituencies as far as possible, as it does not consider that it would be appropriate to start from a ‘blank sheet of paper’. However, this does not mean that an existing constituency should be automatically considered to be ‘protected from change’, simply on the basis of its electorate figure already falling within the statutory range. The changed number of overall constituencies allocated to most English regions, together with the hard limits of the statutory permitted electorate range, means that many constituencies that have an electorate within the statutory range will, nonetheless, need to be altered to create viable constituencies in the surrounding area, and accommodate the new total of constituencies for the region overall.
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Interplay of the considerations

  1. The policy of the BCE is to take into account all the factors listed in Rule 5 as far as possible, subject to the primacy of the permitted electorate range under Rule 2.
  2. The Act does not require the BCE to seek to achieve constituency electorates that are ‘as close as possible to’ the UK electoral quota. Nor does the BCE consider it appropriate to superimpose on the statutory scheme a policy objective of trying to minimise divergence from the UK electoral quota. The desirability of such an aim was specifically raised during the passage of the most recent legislation, and Parliament chose not to add it to the factors to which we may have regard. Not least, such an objective would actually conflict with – and reduce the ability of the BCE to have regard to – the existing factors listed in Rule 5. By way of illustration, the BCE would prefer to identify a constituency that had, say, a 4% variance from the UK electoral quota, but which respected local ties, in preference to an alternative that produced a constituency with only a 1% variance, but which would split communities.
  3. As far as possible, the BCE seeks to create constituencies:
  • from wards that are adjacent to each other; and
  • that do not contain ‘detached parts’, i.e. where the only physical connection between one part of the constituency and the remainder would require travel through a different constituency.
  1. Where it is necessary to have a constituency that crosses a local authority boundary, the BCE will generally seek to avoid having a single ‘orphan’ ward from a local authority isolated in a constituency. This is to avoid the perception (if not the reality) that the residents of that ward – and the local authority of which it remains a part – may be considered less important than the remainder of the constituency by its MP.
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Factors the BCE will not consider

Impact on future election results

  1. The BCE is a politically independent and impartial body. It emphasises very strongly that existing voting patterns and the prospective fortunes of political parties should not and do not enter its considerations during a review.

New local government boundaries

  1. As mentioned above, the local government boundaries that the BCE may have regard to for this review are those that existed or – where relevant – were in prospect (due to being made by an as-yet-unimplemented Order) as at 1 December 2020. Consequently, the BCE will not generally take into account new boundaries after this date.
  2. However, in the limited circumstances where the BCE may be considering the splitting of a ward (as it existed or was in prospect on 1 December 2020) between constituencies in order to meet the statutory electorate range, in considering how to split that ward, the BCE is prepared to take into account, as appropriate, any new ward boundaries introduced after 1 December 2020.

Changes to electorates after the review date

  1. The BCE is required to work on the basis of the numbers of Parliamentary electors on the electoral registers as at 2 March 2020. It is unable to take account of any under-registration or over-registration of electors that may be claimed in some areas.
  2. However, the BCE does not take the view that it is obliged to shut its eyes entirely to growth (or decline) that has occurred since the review date, which it may be aware of from the annual updates of electorate figures it receives, or that it is satisfied is likely to occur. Such a factor may be taken into account in choosing between two or more competing options for the same area that satisfy the statutory rules.
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Naming and designating constituencies

  1. In making its recommendations, the BCE is also required by the Act to specify a name and designation for each proposed constituency. The Act contains no guidance on these points.


  1. The BCE’s policy on the naming of constituencies is that, when constituencies remain largely unchanged, the existing constituency name should usually be retained. In such cases, constituency names are likely to be altered only where there is good reason for change (for example where a constituency named for its main population centre has, over time, seen that main population centre change).
  2. Generally, the BCE considers that the name should normally reflect the main population centre(s) contained in the constituency, as that will likely be the main focal point for communities in the area. However, if a suitable alternative name is proposed which generally commands strong support locally, the BCE will usually be prepared to recommend that alternative.
  3. The BCE adopts compass point names when there is not a clear population centre or other focal point in the constituency. The compass point reference used will generally form a prefix in cases where the rest of the constituency name refers to the county area or a more rural council area (e.g. district), but a suffix where the rest of the name refers to a population centre or essentially urban council area (such as metropolitan or London boroughs, and urban unitaries). Examples of existing constituencies that demonstrate these principles are North Shropshire and Reading West.


  1. The Act also requires that each constituency is designated as either a ‘county constituency’ or a ‘borough constituency’. The BCE considers that, as a general principle, where constituencies contain more than a small rural element they should normally be designated as county constituencies. In other cases, they should be designated as borough constituencies. The designation is suffixed to the constituency name and is usually abbreviated: BC for borough constituency and CC for county constituency.
  2. The designation generally determines who shall act as Returning Officer for Parliamentary elections. The Returning Officer in borough constituencies is a district or borough council chairman or mayor. For county constituencies it is the high sheriff.
  3. The designation also determines the limit on the amount that a candidate is allowed to spend during a Parliamentary election in the constituency. The limit is slightly lower in borough constituencies, to reflect the lower costs of running a campaign in a more geographically compact urbanised area.
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