David Cameron has signalled his intention to press ahead with a Commons vote on redrawing the parliamentary boundaries, despite a warning his Liberal Democrat coalition partners intend to wreck the plan.
Deputy Prime Minister Nick Clegg announced on Monday that he would be ordering his MPs to oppose the new boundaries after a vote by Tory backbenchers derailed his plans to reform the House of Lords.
The proposals to cut the number of parliamentary seats while realigning the boundaries to ensure they have roughly equal numbers of voters is widely seen as the key to the Conservatives chances of outright victory at the next election, giving them up to 20 additional seats.
Visiting an activity centre in mid-Wales, Mr Cameron made clear he intended to push forward with the changes when they come back to the Commons in the autumn, even though he faces almost certain defeat with the Lib Dems lining up with Labour.
"We want the boundary change vote to go ahead," he told reporters. His decision will effectively force Lib Dem ministers to vote against their own Government - throwing the divisions within the coalition into sharp relief.
The Prime Minister - who told Mr Clegg on Monday he could persuade sufficient numbers of Tory MPs to back Lords reform - said it was clear that it was not going to succeed.
"It became quite clear to me that the Labour Party and others in Parliament were not going to allow Lords reform through," he said, adding: "I was not going to have months and months of wrangling."
Mr Cameron said dropping Lords reform would at least give ministers "the space to make the economy the Government's number one priority".
Earlier, however, Lib Dem Foreign Office Minister Jeremy Browne insisted Lords reform and boundary changes were part of the same "constitutional package" and should both be abandoned.
Mr Browne confirmed that he was prepared to vote against the boundary changes: "What has become clear is that the two parties cannot agree on that constitutional reform package and it seems to me to make sense that if there's an area we can't agree on, we put that to one side, we accept that we can't agree on that and we get on with working together on all the areas we can agree on."