Welsh MPs face cut from 40 to 29 in Parliament review
Wales will lose more than a quarter of its MPs under a review of boundaries.
The number will fall from 40 to 29 at the next general election as the UK total is cut from 650 to 600.
Rules require broadly equal numbers of voters in each constituency, with seats in Wales currently having fewer voters on average than those in England.
Changes which would have cut the number of Welsh MPs from 40 to 30 were blocked by the Lib Dems in 2013 after an outcry from Labour.
The revised proposals released on Wednesday are based on new figures on the electoral register.
The Boundary Commission for Wales said it would publish "initial proposals" for Welsh constituencies later in 2016, to be followed by a period of consultation.
The average size of the electorate per constituency across the UK is 74,769, with the electorate of each constituency having to be within 5% of that - meaning each must have between 71,031 and 78,507 voters.
Under the proposals, England will lose 32 MPs, Northern Ireland one and Scotland six to create a smaller House of Commons.
Labour's Shadow Welsh Secretary Nia Griffith said the "substantial cut" in the number of Welsh MPs would "lessen Wales' voice in Westminster at exactly the same time that government policies are hitting the communities we represent".
"If the Conservatives were serious about cutting the cost of politics they would cut the number of unelected peers in the House of Lords, which has ballooned in size with 236 new peers appointed since David Cameron became prime minister," she said.
Plaid Cymru MP Jonathan Edwards MP said: "Westminster will still be responsible for major areas of policy affecting Wales, and our nation will have less of a voice if these proposals go through.
"Unless those major policy areas are devolved, it is a disgrace that our nation should have its voice at Westminster muted in this way."
Scotland previously saw a cut from 72 MPs to 59 at the 2005 general election in response to the shift of powers since devolution.