The disagreement between David Cameron and Nick Clegg appeared to deepen today when the prime minister insisted there was no deal over House of Lords reform.
Clegg claimed on Monday that Lords reform was the Tory offering in exchange for Liberal Democrat support over the constituency boundaries review, but Cameron is now insisting the actual deal was over the AV referendum.
"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," he said.
"Now Nick takes a different view, he's entitled to do that."
The comments suggest the disagreement between the two men has become quite heated and includes a fundamental discrepancy over their memory of what was said during the coalition negotiations.
Neither man will allow the row to permanently shatter the coalition, however.
"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," Cameron told LBC radio.
The prime minister still intends to push through the boundaries review, although it is far from clear he will be able to given opposition from Labour, Liberal Democrats and most smaller parties.
If he is to have a hope it will be by convincing Northern Ireland MPs to come onside – or forcing Clegg to back down from his threat.
"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?'."