The new constituencies in Wales and why they are changing

The number of MPs in Wales will fall from 40 to 32 at the next general election

Many Westminster seats will change radically at the general election under plans to cut the number of MPs in Wales from 40 to 32.

The boundary commission announced last year that several Welsh seats would vanish in their current form.

With the exception of Ynys Môn, every Westminster constituency in Wales will see changes.

These come into into effect when voters go to the polls on Thursday.

First up - what is a constituency?

Wales is represented in two parliaments - one in Cardiff and one in Westminster.

In Westminster, Members of Parliament (MPs) hold seats which represent constituencies.

These are areas of the country which have defined boundaries, which have been decided by impartial boundary commissions.

What are the new constituencies in Wales?

• Aberafan Maesteg

Aberafan is being merged with Maesteg, to form the Aberafan Maesteg seat.

• Alyn and Deeside

A constituency will still exist called Alyn and Deeside, including the whole of the existing consistency, but with added wards from Delyn, including Flint and Bagillt.

• Bangor Aberconwy

Part of Arfon, including wards that cover the city of Bangor, and some areas in Clwyd West such as Llansannan, will merge with Aberconwy to form Bangor Aberconwy.

• Blaenau Gwent and Rhymney

Blaenau Gwent will be extended to cover areas in the Rhymney valley.

• Brecon, Radnor and Cwm Tawe

The rural seat of Brecon and Radnorshire is being expanded to parts of the existing Neath constituency, in the Swansea Valley, including Ystalyfera and Pontardawe. The new seat will be called Brecon, Radnor and Cwm-Tawe.

• Bridgend

Porthcawl and Pencoed will now be included in the constituency of Bridgend.

• Caerfyrddin

The new seat of Caerfyrddin covers all of northern Carmarthenshire, including the town of Carmarthen.

• Caerphilly

A seat called Caerphilly will remain with revised boundaries, including a small part of the Islwyn constituency.

• Cardiff East

The existing seat of Cardiff Central will be scrapped.

A new seat called Cardiff East will include part of the old constituency, as well as some parts of Cardiff South and Penarth.

• Cardiff North

Cardiff North will retain its name but gain the ward of Taffs Well.

• Cardiff South and Penarth

The new Cardiff South and Penarth seat will extend all the way from Penarth to Cathays, and will also include Dinas Powys for the first time.

• Cardiff West

A Cardiff West seat will remain. It will gain a number of wards from Pontyclun, Rhondda Cynon Taf.

• Ceredigion Preseli

Ceredigion will be extended out west to include parts of Fishguard, in a seat called Ceredigion Preseli.

• Clwyd East

The boundaries of Delyn, Clwyd West, Clwyd South and Vale of Clwyd vanish in the new map.

Much of the Delyn constituency, including Mold, Gronant and New Brighton, will form the new Clwyd East.

The new seat will also include Prestatyn from Vale of Clwyd, Llangollen from Clwyd South and Ruthin from Clwyd West.

• Clwyd North

Rhyl, Bodelwyddan, Denbigh and St Asaph from Vale of Clwyd will be joined together with parts of Clwyd West - including Colwyn and Towyn - to form Clwyd North.

• Dwyfor Meirionnydd

The constituency of Arfon will cease to exist. Parts of it, including Caernarfon and Llanberis, will join Dwyfor Meirionnydd.

• Gower

The Gower constituency will include all but one of the council wards from the existing seat of the same name, plus five wards from the existing Swansea West seat, including Killay.

• Llanelli

The town of Llanelli will still have a seat named after it, including four wards from Carmarthen East and Dinefwr.

• Merthyr Tydfil and Aberdare

As the name suggests, Merthyr Tydfil and Aberdare will include both of the towns.

The Cynon Valley constituency will disappear, split between Merthyr Tydfil and Aberdare, and Pontypridd.

• Mid and South Pembrokeshire

The two existing Pembrokeshire constituencies will be scrapped. A new seat, called Mid and South Pembrokeshire, will cover Milford Haven, Pembroke Dock, Tenby and Haverfordwest.

• Monmouthshire

Monmouth will be renamed Monmouthshire with more of the Severnside area added, including the town of Caldicot.

• Montgomeryshire and Glyndŵr

Montgomeryshire will be combined with council wards from parts of Clwyd South, including Chirk North and South, and Penycae, to form Montgomeryshire and Glyndŵr.

• Neath and Swansea East

Neath and Swansea East will include most of the existing seat of Neath and three wards from Swansea East, including Llansamlet.

• Newport East

Newport will still have a Newport East constituency, although it will incorporate parts of what is currently in Newport West, including Caerleon and Pillgwenlly.

• Newport West and Islwyn

Much of the old Newport West will be incorporated into Newport West and Islwyn, which will include the valley to the north of the city, up to Blackwood.

• Pontypridd

The new Pontypridd seat will include much of the old one, including the town itself and Talbot Green, as well as three wards from the current Ogmore seat including Llanharan, and parts of the former Cynon Valley seat including Abercynon and Mountain Ash.

• Rhondda and Ogmore

The Rhondda seat and part of the old Ogmore constituency are being merged into a single area.

• Swansea West

The old Swansea West is formed from what is left of Swansea West - Castle, Sketty, Townhill and Uplands - and parts of Swansea East.

• Torfaen

A slightly-expanded constituency called Torfaen will remain, including parts of Cwmbran that were in Monmouth previously.

• Vale of Glamorgan

An amended Vale of Glamorgan seat will still exist, but without the Dinas Powys ward, which will become part of Cardiff South and Penarth.

• Wrexham

Wrexham will be expanded to take more of the council area, including New Broughton and Overton.

• Ynys Môn

Because of its protected status Ynys Môn - which covers Anglesey - will remain a standalone constituency.

Why are these changes happening?

The changes came about after a review by the boundary commission, which ended last year.

Seats in Great Britain have within them between 69,724 and 77,062 voters.

But up until now Wales has had some of the smallest constituencies in the UK - and on average they are smaller than those in England.

For example Arfon, according to 2020 figures, had just 40,999 voters - the smallest constituency on mainland Great Britain by electorate.

It was inevitable that some constituencies would have to be significantly withdrawn.

The changes to the electoral boundaries were triggered by the Conservative UK government

The shake-up was triggered by the Conservative UK government in a bid to make constituencies roughly the same size, while keeping the overall number of MPs the same.

They argued that it would make everyone's vote fairer, because it would give each vote roughly equal worth as a vote in another constituency.

The process has been a major overhaul - the Boundary Commission for Wales said it was the most significant change to Wales' Westminster constituencies in a century.

Why do the changes matter?

Unless you live in Ynys Môn, the constituency and the area that your MP represents will change.

Opponents of the boundaries review have argued that the changes will leave Wales with less of a say in Westminster, with fewer MPs representing its interests.

There have been concerns from Labour that the way the changes have been carried out could break community ties.

Meanwhile Plaid objected to Wales having, what they argued, was a "20% reduction in our democratic voice".

Will fewer MPs affect the Senedd?

The new boundaries will be used by the Senedd to draw up the 16 constituencies of the next Welsh Parliament.

Each constituency will be paired with another, and will be served by six MSs elected through a list system.

The Senedd changes have been approved and will come into effect at the next election in 2026.