This week's referendum on voting reform will change the nature of the coalition Government, regardless of its result, Deputy Prime Minister Nick Clegg said today.
Mr Clegg said the May 5 poll will mark the end of the "first phase" of the Conservative/Liberal Democrat coalition, which required "real collective discipline", and will allow the parties to express their differences more openly in future.
But Prime Minister David Cameron insisted that the Government remains "very cohesive and strong", and is able to continue to deal with issues such as the deficit, terrorism and public service reform in a united way, despite its increasingly vitriolic inter-party spat over the alternative vote system (AV).
The campaign on whether to replace the first-past-the-post system for electing MPs with the alternative vote - under which voters rank candidates in order of preference - has been marked by brutal exchanges between the coalition partners, with Lib Dem minister Chris Huhne even threatening Cabinet colleagues with legal action for alleged untruths.
Mr Cameron declined today to come to the defence of the tactics of the No to AV campaign, which has infuriated his Lib Dem colleagues by targeting Mr Clegg personally.
The Prime Minister said he would take responsibility only for the Conservative No campaign - which has focused on the argument that first-past-the-post is "simple, fair and decisive" - and not for the cross-party No to AV camp's more "robust" approach, even though pro-reform campaigners argue it is largely funded from Tory sources.
Speaking on BBC Radio 4's Today programme, Mr Clegg made clear that his Liberal Democrats expect to take a more independent approach to government after Thursday's vote.
"I think that the first phase of this coalition - the first year, as we were making really difficult decisions on the deficit and so on - required real collective discipline," he said.
"But over time, inevitably, the different identities, different values of the two parties - because we are different parties, always have been always will be - would kind of come out in the wash a bit more.
"And I think that is probably happening in part because of this referendum."
But Mr Cameron insisted there was no reason to expect the coalition to fall apart.
He told Today: "The reason for being in a coalition is as good today as it was a year ago. That is because we are dealing with a serious economic situation, with a massive budget deficit, huge debts that we need to deal with.
"Two parties that are different have come together in the national interest to sort out the economy and to deliver the coalition agreement, which includes also some radical and bold reforms of things like our schools and welfare system.
"This was always going to be a difficult moment, with the two parties on different sides of the referendum campaign.
"But we have a Cabinet meeting this morning, we have a National Security Council meeting afterwards, at the Cobra meeting last night there were Liberal Democrats and Conservatives working out how to keep the country safe from terrorists, at the same time as having a robust argument about the future of the voting system.
"We are getting on with dealing with the problems our country faces and I think been a very cohesive and very strong Government."