The increasingly bitter AV campaign spilled over into Government business for the first time today after Chris Huhne raised Conservative tactics in a meeting of the Cabinet.
Mr Huhne challenged the Prime Minister and Chancellor to state their position on the tactics being used by the cross-party No2AV campaign.
However Mr Cameron refused to be drawn into a discussion and dismissed Mr Huhne’s behaviour as ‘inappropriate’ during an official government meeting. Sources described the moment as ‘a bit of a bust up’.
The row was later fuelled by the Lib Dem Foreign Office minister Jeremy Browne. He said he was amazed that modernizing Tories hadn't counseled the Prime Minister that the vitriol surrounding the campaign could do long term damage to his own repositioning of the Tory brand.
Browne said the party had moved "quite a long way backwards" towards the nasty party image during the AV campaign, and said such divisive action could leave the coalition looking "a bit different" after the referendum.
Earlier in day Deputy Prime Minister Nick Clegg admitted for the first time today he was ‘naïve’ to think the Alternative Vote referendum would not cause cracks in the Coalition government.
In an interview on the Today Programme Mr Clegg said he had hoped that the debate on AV would rise above party politics.
But in a sign of how fractious the debate has become Prime Minister David Cameron used an interview on the same programme to defend the tactics used by the No2Av campaign which have infuriated Liberal Democrats.
Meanwhile Labour has not escaped the fall out from the increasingly bitter rows over AV.
The former leader Neil Kinnock today launches an outspoken attack in The Independent on senior colleagues in his party who have campaigned with the Conservatives to encourage a ‘No to AV’ vote on Thursday.
Mr Kinnock told The Independent he "simply cannot understand" how John Reid, Margaret Beckett, John Prescott and David Blunkett can back the Conservatives in support of a system which kept Labour out of power for decades.
"I simply cannot understand how experienced colleagues can mistake the lessons of the last 60 years: that the Tories have profited massively from divisions in the continual anti-Tory majority," he said. "They must recognise the implacable truth – that first past the post is the Tories' lifeline."
In his interview on the BBC 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 has allowed the parties to express their differences more openly in future.
"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."
He added: “I expected, perhaps naively with hindsight, that it wouldn’t be an argument waged by politicians sitting in radio and television studios, and it wouldn't be seen through the prism of party politics.”
But Mr Cameron was keen to reassure voters that there was no reason to expect the coalition to fall apart. He insisted that the Government remains "very cohesive and strong", and is able to continue to deal with the issues that define our generation.
He told Today: "The reason for being in a coalition is as good today as it was a year ago.. 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."