David Cameron said that he had a "fundamental disagreement" with Deputy Prime Minister Nick Clegg over the Government's constitutional reforms, but insisted it would not stop them working together in coalition.
The Prime Minister rejected Mr Clegg's claim that the Conservatives had broken the coalition "contract" by failing to support House of Lords reform, forcing the Liberal Democrat leader to abandon his plans for a mainly-elected upper chamber.
Interviewed on LBC 97.3 radio, Mr Cameron insisted the only deal had been for the Tories to allow a referendum on AV voting for parliamentary elections in return for Lib Dem backing for a re-drawing of the parliamentary boundaries.
"There's a fundamental disagreement here in that I profoundly believe that the link was between the AV referendum that we promised to deliver and the boundary changes that I think are right because you should have equal-sized seats across the country," he said.
"Now Nick takes a different view, he's entitled to do that, but as I say, this disagreement is not going to get in the way of getting on with what really matters, which is getting people back to work, getting our economy moving, getting investment in Britain."
Despite Mr Clegg's warning that the Lib Dems would now line up with Labour to oppose the boundary changes - which experts believe could be worth an extra 20 seats to the Tories at the next general election - Mr Cameron made clear that he would fight to push them through when they come back to the Commons next year.
"We've got a lot of water to flow under the bridge between now and then," he said.
"Every MP is going to have to ask themselves 'Why am I voting against equal-sized constituencies and a smaller House of Commons?'.
"People listening to this programme would love us to cut the size of the House of Commons, stop spending so much money on politics and have a fair system where all the seats are the same size. That's what they can vote for when the boundary vote comes through."