Nick Clegg tonight laughed off rumours that one of his predecessors as Liberal Democrat leader was defecting to Labour.
The Deputy Prime Minister said the suggestion that Charles Kennedy was quitting in protest at the coalition deal was the "silliest of silly-season stories".
The long-serving MP is believed to be upset over the policy compromises made to form the alliance with the Tories, and especially the deep spending cuts that have been proposed.
He refused to endorse the coalition deal when it was put to a vote of the parliamentary party in May, preferring a tie-up with Labour.
Labour leadership contenders today said defections from the Lib Dems would be "no surprise", but insisted they had not held any discussions with the Ross, Skye and Lochaber MP.
And on a visit to Bristol, Mr Clegg said he had received an email from Mr Kennedy reassuring him there was no basis to the rumours.
"It's nonsense, it's not true," Mr Clegg insisted. "Not taking it seriously is putting it seriously mildly.
"I can't do better than say what Charles has said which is that it's the silliest of the silly-season stories, its just nonsense so I'm not going to waste any more time on it."
He went on: "I think people want to look for cracks and divisions and tensions where they don't necessarily exist.
"Are there people who are concerned about how the coalition is operating in the Conservative party?
"Yes I should think so and there are in the Lib Dem party as well, that's normal.
"We're doing something very different and new but I think people in the Lib Dems know that we have entered this coalition for a five-year period and that the time to judge if it's been a success or not is not in the heat and fury of daily headlines after 100 days, it's after 5 years. We're governing for the long term, for the long-term benefit of the country as a whole."
The rumours about Mr Kennedy - who was Lib Dem leader between 1999 and 2006 - resurfaced amid slumping poll ratings for the party, and grassroots dismay at the partnership with the Tories.
Mr Clegg has rejected fears that his party was being damaged by the alliance - bluntly stating that no one would be taking "any notice" of the Lib Dems if it was not in government.
However, he has explicitly ruled out any electoral pact with the Conservatives at the next general election, scheduled for 2015.
This week saw Mr Clegg's deputy, Simon Hughes, harden his position as a standard bearer for the Lib Dem left.
He said his party should get a veto on policies from the coalition Government, and also indicated that a partnership between the Lib Dems and Labour was still possible.
Writing on his blog today, Labour education spokesman Ed Balls said: "If these rumours are true, then it would be very welcome.
"And it would be no surprise because we've already seen thousands of Liberal Democrat supporters and members coming over to Labour since the election.
"Canvassing in the local by-election in Edinburgh yesterday it was striking how many people said they'd voted Lib Dem at the general election but never would again."