The Westmorland and Lonsdale MP Tim Farron today denied he had ambitions to lead the Liberal Democrats.
Asked if he would accept the job if offered it, Mr Farron said "certainly not".
Mr Farron, who is the party's president, has often been tipped as a potential future Lib Dem leader.
He raised eyebrows at the party's Birmingham conference on Sunday with an outspoken attack on their Conservative coalition partners - saying they would be "an absolute nightmare" if governing alone.
In an interview for BBC2's Daily Politics today, Mr Farron was challenged over whether he was positioning himself to take over the leadership when Nick Clegg's time runs out.
He replied: "I have no such ambition."
Asked by interviewer Andrew Neil whether he would accept the leadership if offered, he replied: "Certainly not".
And when Neil followed up: "You would refuse it?", he responded swiftly: "Yes."
"It is not going to come up," said Mr Farron.
"Nick Clegg is doing a brilliant job. not only is Nick Clegg doing a great job, but he is also a mate and somebody who deserves support."
Mr Farron acknowledged he had heard a joke which has been circulating among delegates at Birmingham: "Who does Tim Farron want to be when he grows up? Simon Hughes."
But he insisted there was nothing wrong in being compared to Mr Hughes, who has long been seen as the voice of the Lib Dem left without ever winning the party leadership.
"Everybody's ambition should be to be like Simon," joked Mr Farron.
Mr Farron also admitted feeling "uncomfortable" that his party's conference includes supermarket giants Asda and Tesco among its sponsors.
"I take the view that Asda and Tesco have huge questions to ask about the way they treat farmers," he told BBC North West.
"You ask me, am I personally uncomfortable about being at a conference that is sponsored by people I think have damaged my farmers?
"Too right I am."
But he added: "A lovely phrase from the Salvation Army days: 'I'm quite happy to take dirty money and clean it'. So here we go."
Mr Farron, a former Lib Dem agriculture spokesman, said he did not blame the supermarkets for "exploiting" farmers as it was the system that was at fault.
He welcomed the Government's commitment to introduce a new watchdog.