Senior Liberal Democrat Lord Ashdown has launched a scathing attack on Prime Minister David Cameron for his conduct during the electoral reform referendum campaign.
In the first sign of recriminations between the coalition parties, the former Lib Dem leader - a close ally of Nick Clegg - accused Mr Cameron of a "breach of faith" in permitting a largely Conservative-funded No campaign which targeted the Deputy Prime Minister personally.
While Lord Ashdown said the coalition would survive, he made clear that the nature of the campaign would change the atmosphere of the Conservative/Liberal Democrat partnership.
In an interview with The Times, Lord Ashdown said: "You cannot fund a deeply vicious campaign to destroy the personality of your partner, who has been unmoved in his brave support of the coalition, without there being consequences. When it comes to the bonhomie of the Downing Street rose garden, it's never again glad confident morn."
Lord Ashdown - who appeared effectively to concede defeat in the electoral reform battle - said any other prime minister would have dissociated himself from what he called "a regiment of lies" produced by the No campaign, which accused Mr Clegg of broken promises on tuition fees and spending cuts and argued that the alternative vote was a "Lib Dem fix".
He accused the PM of "panicking" in the face of Tory pressure when the Yes campaign secured early opinion poll leads, and going back on a "private agreement" with Mr Clegg on the way the referendum would be fought.
"In backtracking, to use no stronger a word than that, on what was a private agreement he had with Nick Clegg about the way this campaign was conducted, I think the Prime Minister panicked in the face of his right-wingers. I regret that," said the Lib Dem peer.
Lord Ashdown dismissed suggestions that the tensions between Lib Dems and Tories might bring the coalition to a premature end. In a warning to activists, he said the Lib Dems must "stick with" the arrangement and see out the planned five-year full term.
"We set our hand to a task we never believed would deliver popularity for the party," he told The Times. "It was in the national interest.The underlying purpose of the coalition remains. Liberal Democrats must stick with it. There's a job to be done and we must see it through."
But he said Lib Dems are "exceedingly angry" and there would be consequences for the coalition. "What that means is that this is a relationship that is much less about congeniality, it becomes a business relationship, a transactional relationship, and maybe it will be all the better for that."