Welsh MPs are pondering their political futures after the unveiling of plans to cut the number of parliamentary seats in Wales by a quarter.

If approved, it would mean the end of historic county constituencies such as Anglesey and Montgomeryshire.

Boundary Commission proposals to cut Wales's 40 MPs to 30 hail the biggest change in the political map since 1944.

The plans, which follow UK government legislation, are open to public consultation until 4 April.

If given the go-ahead, they would bring changes to the constituency map in every part of Wales.

A reduction in the number of seats in north Wales would see the end of constituencies like Delyn and Clwyd West and the establishment of new seats such as North Wales Coast, Dee Estuary and Wrexham Maelor.

The changes would have repercussions for MPs, including Wales Office minister David Jones, who would see the end of his Clwyd West seat.

Mr Jones might have to fight for the Conservative nomination in a new seat of North Wales Coast, possibly against current Aberconwy Tory MP Guto Bebb.

Elsewhere in the north west, Anglesey would join parts of the mainland around Bangor to form the new constituency of Menai ac Ynys Mon.

Analysis Labour have used the G-word - gerrymander - but are privately relieved that their high-profile MPs should be able to avoid fighting each other in brutal selection contests for new seats. Where Labour-held seats disappear, natural retirements or the House of Lords may offer a way out. Plaid Cymru have highlighted some of the arguments put forward when the cut was initially suggested - that villages in the same community are being split and other communities are being joined despite being separated by mountains. The Liberal Democrats face uncertain futures in their heartlands, but life is more complicated for their Conservative coalition partners, the architects of the cut in MPs. The Wales Office minister David Jones - the only Welsh Tory currently a departmental minister - will see his Clwyd West seat dismembered. There is a potential battle in Pembrokeshire between the government whip Stephen Crabb and Simon Hart. Glyn Davies, parliamentary private secretary to the secretary of state for Wales, whose Montgomeryshire seat is carved up, said he was "hugely disappointed by the changes".

The disappearance of the seats of Ynys Mon and Arfon might raise eyebrows within Plaid Cymru, who are strong challengers in both.

Plaid's Arfon MP, Hywel Williams, could find himself fighting for selection in the new Gwynedd seat against his colleague Elfyn Llwyd, the MP for Dwyfor Meirionnydd.

"I find the rationale behind some of the changes quite puzzling, and certainly it will be difficult to represent some of these communities who have no links in the past with each other," said Mr Williams.

Plaid Cymru was also concerned about the increased size of some seats, and the ability of MPs to keep in touch with constituents across large rural areas.

Tory MP Glyn Davies's Montgomeryshire seat would also disappear, to become part of a wider south Powys constituency, currently represented by Liberal Democrat Roger Williams.

But Mr Davies said he still supported the boundary proposals.

"There were commitments to reduce the numbers of MPs. I stood on that at the General Election as policy and when it came before us as Members of Parliament I voted for it, he said.

The seats of Conservative MPs Stephen Crabb in Preseli Pembrokeshire and Simon Hart in Carmarthen West and South Pembrokeshire would also be broken up with parts included in a new seat of South and West Pembrokeshire.

The Tories also look set to lose out with the proposed merger of Cardiff North with Caerphilly.

Voice 'diluted'

Labour faces the loss of strongholds in the south Wales valleys with Cynon Valley combining with Merthyr Tydfil, while Aberavon and Ogmore would merge.

Huw Irranca-Davies, the Labour MP for Ogmore, told BBC Radio Wales the proposed changes would reduce Wales' influence at Westminster.

Changes under the proposals There would be 30 new parliamentary constituencies: Menai ac Ynys Mon; Gwynedd; Ceredigion and North Pembrokeshire; South and West Pembrokeshire; Caerfyrddin; Llanelli; Gower and Swansea West; Swansea East; Neath; Aberavon and Ogmore; Bridgend; The Vale of Glamorgan; Cardiff West; Cardiff Central and Penarth; Cardiff East; Caerphilly and Cardiff North; Newport West and Sirhowy Valley; Newport Central; Monmouthshire; Torfaen; Blaenau Gwent; Heads of the Valleys; Rhondda; Pontypridd; South Powys; Glyndwr and North Powys; Wrexham Maelor; Alyn and Deeside; Dee Estuary; and North Wales Coast.

15 existing constituencies would be wholly contained within a new constituency: Alyn and Deeside; Blaenau Gwent; Brecon and Radnorshire; Bridgend; Cardiff West; Ceredigion; Dwyfor Meirionnydd; Llanelli; Merthyr Tydfil and Rhymney; Neath; Rhondda; Torfaen; Vale of Glamorgan; Wrexham and Ynys Mon.

There would be six constituencies over 1,000 sq km: Caerfyrddin, Ceredigion and North Pembrokeshire, Glyndwr and North Powys, Gwynedd, South and West Pembrokeshire, and South Powys.

10 of the existing names would be retained

Source: Boundary Commission for Wales

"Wales is going to have 10 voices less in Westminster and that means 10 less MPs on committees, doing work, speaking in debates, lobbying ministers," he said.

"I say that of all political parties because I think the Liberals and the Tories are going to lose out here as well as Labour."

Mr Irranca-Davies added that while the changes might be "arithmetically fair" they would not be fair to Wales in not recognising its national status.

He said: "It's more to do with the voice of Wales as a nation in Westminster. And that today has been diluted."

Across Cardiff there would be a reduction of one seat. The Liberal Democrat stronghold of Cardiff Central would be no more and new seats would include Cardiff East as well as Cardiff Central and Penarth.

Geographical factors

The plans meet criteria set by the Parliamentary Voting System and Constituencies Act of 2011.

Each constituency's electorate must number between nearly 73,000 and just over 80,000 voters.

Document Boundary Commission proposed map of changes [6.7Mb] Most computers will open PDF documents automatically, but you may need Adobe Reader Download the reader here

This is much higher than the number of people in most existing Welsh constituencies, so their number must reduce by 10.

Across the UK the number of constituencies will reduce from 650 to 600.

In drawing up the plans the commission has given consideration to geographical factors and to existing local government boundaries where possible.

But its report makes clear it was "frequently necessary" to cross these boundaries to form constituencies that comply with the statutory electorate range.

As an independent and impartial body, the Boundary Commission has emphasised "very strongly that existing voting patterns and the prospective fortunes of political parties do not enter its considerations."

Document Map of existing Welsh constituencies [6.7Mb] Most computers will open PDF documents automatically, but you may need Adobe Reader Download the reader here

Secretary to the commission Ben Whitestone said: "People may write in or e-mail us to let us know what they think of the commission's proposals - whether they accept or object - we are keen to hear people's views.

"Where people object - particularly where they can supply counter proposals - the commission will give full consideration and may amend its proposals accordingly."

The commission's final proposals will be submitted to parliament by 1 October 2013.