Welsh MPs are braced for proposals being announced tomorrow to slash their ranks by 25 per cent.
The Boundary Commission for Wales will be spelling out how it plans to reduce the number of the principality's Westminster constituencies from 40 to 30.
This is part of a UK-wide package to cut the MPs' total to 600, down from the current 650, in a coalition Government bid to iron out discrepancies.
Commissioners are required to keep constituency electorates within 5 per cent of the UK average - with a 72,810 floor and an 80,473 ceiling.
Welsh rural constituencies could be among the most vulnerable under the changes in contrast to elsewhere in the UK where urban areas have tended to lose out.
North west Wales currently returns MPs for Aberconwy, Arfon, Clwyd West, Dwyfor Meirionnydd and Ynys Mon but their combined electorates would only qualify for three seats under the rules imposed on the commission.
Ynys Mon is not protected by its island status and, unlike the Isle of Wight, Na h-Eileanan an Iar and Orkney and Shetland, will have to take in territory from the mainland.
It will be difficult for media, political and academic experts to make definitive predictions of the shake-up's effect on party performance until at least 2013.
The speeded-up consultation and review process will involve examination by the commission of written representations on its initial proposals and comments in public hearings.
It will then produce revised plans.
Further written representations will be considered on these before the commission draws up final recommendations.
Final reports have to be sent to Parliament by October 2013.
Provisional proposals for England, Scotland and Northern Ireland were announced last year.