Senedd constituencies

History

Establishment

Following the 1997 Welsh devolution referendum, where a narrow majority voted in support of the creation of a devolved Welsh Assembly, constituencies of the devolved legislature were established.

Section 2 of the Government of Wales Act 1998 stipulates that the constituencies for the National Assembly for Wales be the same as the constituencies used for elections to the United Kingdom Parliament. The same act sets out the creation of five regions which would use the same borders as the five European Parliamentary constituencies in Wales which themselves were set out in the European Parliamentary Constituencies (Wales) Order 1994, used for elections to the European Parliament between 1994 and 1999. The electoral regions set out are still used, despite the abolishment of the five European Parliamentary constituencies for an all-Wales constituency, and the withdrawal of the UK from the European Union. Although minor border adjustments to the regions have taken place.

2007 change in boundaries

In 2006, the Government of Wales Act 2006 was enacted. When enacted the act reinforced the link between Assembly and UK Parliamentary constituencies, and that the number of electoral regions is five.

Following the fifth periodic review of Westminster constituencies, new borders for the constituencies and electoral regions were defined by the Parliamentary Constituencies and Assembly Electoral Regions (Wales) Order 2006.

The order detailed the abolition of three constituencies (Caernarfon, Conwy, and Meironnydd Nant Conwy), with three new constituencies to replace them (Aberconwy, Arfon, and Dwyfor Meirionnydd). Nine constituencies were subject to "substantial" border adjustments involving the transfer of more than 3,000 inhabitants between constituencies. A further eight constituencies were subject to boundary changes resulting in the redistribution of fewer than 3,000 inhabitants between each constituency, and a further four constituencies were subject to minor boundary adjustments that led to minimal transfers of inhabitants between constituencies. The remaining sixteen constituencies were not subject to any boundary or name modifications.

The three new constituencies straddled the border of the electoral regions of Mid and West Wales and North Wales, leading to adjustments in the boundaries of both electoral regions, in addition to minor adjustments to the constituency of Montgomeryshire also leading to minor regional boundary adjustments. In south Wales, the boundaries of the electoral regions, South Wales West, and South Wales Central were altered to accommodate changes to the boundaries of Bridgend, and Vale of Glamorgan constituencies.

The changes in the boundaries for constituencies and electoral regions of the Senedd came into force for the 2007 National Assembly for Wales election.

Delinking from UK parliament constituencies

Section 13(1) of the Parliamentary Voting System and Constituencies Act 2011 states that:

The Assembly constituencies are the constituencies specified in the Parliamentary

Constituencies and Assembly Electoral Regions (Wales) Order 2006 (S.I. 2006/1041)24 as amended by— the Parliamentary Constituencies and Assembly Electoral Regions (Wales) (Amendment)

Order 2008 (S.I. 2008/1791)

— Parliamentary Voting System and Constituencies Act 2011

This details that any further changes to the UK Parliament constituencies in Wales specified in the act (notably the proposed reduction in constituencies to 30) will not be applied to Assembly (Senedd) constituencies.

In a session of the House of Commons where the then secretary of state for Wales, Cheryl Gillan was questioned on the Labour party's opposition to the decoupling of the two constituencies, she replied:

That is a very interesting thought. Hon. Members are well aware that the Parliamentary Voting System and Constituencies Act 2011 broke the link between Assembly constituencies and parliamentary constituencies. I have agreed that we need to look carefully at the implications of having constituency boundaries relating to different areas and regions for UK and Assembly elections in Wales.

— Rt. Hon Cheryl Gillan MP

Boundaries of Senedd constituencies and electoral regions were initially not overseen by any statutory review body, following the delinking of Senedd and UK Parliament constituencies in 2011. With the responsibility for proposing alterations to the boundaries of UK Parliament constituencies in Wales, and reporting to the UK Government, lay with the Boundary Commission for Wales. At the time, both constituencies had the same boundaries. Organisations such as the Electoral Reform Society Cymru indicated a preference for coterminosity (mirroring Senedd and UK Parliament constituencies, especially during the 2016 proposed reforms). However, such coterminosity was merely desired and was not enforced by law, meaning any changes to UK Parliament constituencies in Wales did not need to be mirrored for Senedd constituencies. The 2023 review of Westminster constituencies reduced the number of UK Parliament constituencies in Wales from 40 to 32, and were used from the 2024 UK election. While the Senedd is to introduce larger constituencies composed of pairings of the 32 from 2026.

2020 renaming

On 6 May 2020, the Senedd and Elections (Wales) Act 2020 came into force, renaming the Assembly constituencies and Assembly electoral regions of the National Assembly for Wales, to the Senedd constituencies and Senedd electoral regions of "Senedd Cymru" or "the Welsh Parliament", known in both Welsh and English as the Senedd.

2024–25 boundary review

The Senedd Cymru (Members and Elections) Act 2024, passed by the Senedd in May 2024, gave the responsibility for conducting boundary reviews of Senedd constituencies to the Democracy and Boundary Commission Cymru. The commission would be responsible to conduct reviews for specifically both the 2026 Senedd election and the 2030 Senedd election, as well as regular reviews thereafter. The 2026 review was time-constricted, therefore the 2030 review, the first full boundary review in 18 years, would provide the commission with more flexibility.

The Senedd Cymru (Members and Elections) Act 2024 legislated that the 2026 election should use 16 six-member constituencies, replacing the existing 40 constituencies and five regions, with the Democracy and Boundary Commission Cymru conducting the review. The law set out that they must be contiguous pairings of the 32 UK Parliament constituencies used in Wales since 2024, and to only use a single name in both Welsh and English, unless it could be considered unacceptable for a single name. The review commenced in July 2024, with initial proposals revealed in September 2024, and revised proposals in December 2024. A major change in the revised proposals was the use of mostly Welsh-language names only to meet the condition in law, therefore all (except four) had only one name, its Welsh name. The decision received support from Cymdeithas yr Iaith, but opposition from Andrew RT Davies, former leader of the Welsh Conservatives. In March 2025, the commission published its final determinations, for the 16 constituencies (see § Proposed constituencies (2026)). The original initial proposal boundaries were re-adopted, while all constituencies were made to use Welsh-only names, with a reiteration of both support and opposition from Cymdeithas and Davies respectively, as well as consultation respondents. By law, the Senedd must put these final determinations into effect for the 2026 Senedd election without alteration.

2030 boundary review

The 2030 boundary review was launched by Democracy and Boundary Commission Cymru on 9 September 2026. It will follow the Local Government (Democracy) (Wales) Act 2013, since amended as the Democracy and Boundary Commission Cymru etc. Act 2013, where the sixteen Senedd constituencies must be within 10% of the electoral quota, so between 90% and 110% of the quota. The electoral register had 2,402,053 people registered, therefore the electoral quota for each constituency is 150,128, so each constituency must be between 135,225 and 165,275 voters. Initial proposals are to be released in early 2027, followed by an 8-week consultation period, with the final determinations to be submitted before 1 December 2028. The new boundaries would replace those used for the 2026 election. The decision to use Welsh-only names for the 2026 constituencies may be revised following public consultation due to the initial decision raising some opposition. Existing legislation still requires a single name to be used where possible, although if no single bilingual name reflecting an area's identity could be found then a bilingual name may be considered.

List of historic constituencies and electoral regions (1999–2026)

Under the Additional Member System in place until May 2026, there were forty single-member constituencies and five four-member regions. The five electoral regions were: Mid and West Wales, North Wales, South Wales Central, South Wales East, and South Wales West; each region roughly contained 500,000 people and each constituency contained a population of around 60,000. The forty constituencies are listed below. The final election under the Additional Member System was the 2025 Caerphilly by-election and the final general election was the 2021 Senedd election, with boundaries that were also used for the Assembly elections of 2007, 2011, and 2016.

Senedd constituencies were grouped into electoral regions consisting of between seven and nine constituencies. An additional member system was used to elect four additional Members of the Senedd from each region, in addition to the MSs elected by the constituencies. The Electoral Region boundaries were based upon the pre-1999 European Parliament constituencies. At each general election of the Senedd, each elector had two votes, one constituency vote and one regional party-list vote. Each constituency elected one Member by the first past the post (single-member district plurality, SMDP) system, and the additional Senedd seats were filled from regional closed party lists, under the D'Hondt method, with constituency results being taken into account, to produce a degree of proportional representation for each region. Altogether, the sixty Members of the Senedd were elected from the forty constituencies and five electoral regions, creating a Senedd of forty constituency MSs and twenty additional MSs, with every constituent represented by one constituency member and four regional members.

The constituencies were the same as those used for elections to the House of Commons of the United Kingdom until the 2024 United Kingdom general election but not linked to them. The borders of each constituency were drawn using Local government boundaries, defined in Parliamentary Voting System and Constituencies Act 2011 as "the boundaries of counties, county boroughs, electoral divisions, communities and community wards".

2007–2026 constituencies

1999–2007 constituencies

Between the first election in 1999 for the then National Assembly for Wales, to the 2007 election, there were three former constituencies. These constituencies were replaced at the 2007 election, with new boundaries and names.

Three constituency names, Conwy, Caernarfon, and Meirionydd Nant Conwy, became historic, and the new boundaries defined three constituencies with new names: Arfon, Dwyfor Meirionnydd, and Aberconwy. Generally, the new boundaries define each constituency taking into account local government ward boundaries, and define constituencies close to equal in terms of the sizes of their electorates.

Former electoral regions