The two men expected to vie to become the next Liberal Democrat leader set out their visions of the party's route to power as unrest continued over Sir Menzies Campbell's performance in the job.
Nick Clegg and Chris Huhne went head to head for the first time at a fringe meeting organised by The Independent, both arguing the party needed to broaden its appeal.
They gave support to Sir Menzies, who has been dogged by sniping over his age and leadership style.
But a senior party figure admitted there had been "rumblings of discontent" among colleagues and Lord Ashdown, the former Liberal Democrat leader, warned Sir Menzies' critics to show some loyalty.
Mr Clegg, the party's home affairs spokesman, admitted the party needed to widen its appeal by offering pragmatic, liberal policies on issues, such as immigration, housing and public services, which preoccupied voters.
He told the meeting: "We need to be restless, we need to be radical, asking those questions the other parties aren't prepared to ask.".
"Of course the Liberal Democrats must always champion the issues for which we are best known – civil liberties, transparency in politics, internationalism and the environment."
But he warned the party had to work out how to make its liberal values relevant to the everyday lives of voters who had never supported the party.
He said: "We retain our core appeal in these core issues. We must be ambitious about our future and reach out into those areas about which we have not been as vocal in the past."
Mr Clegg said the party had to be aware of a series of new challenges. They included maintaining a liberal society at a "time of fear", making public services more responsive to the demands of the "Google generation ", coping with the pressures of globalisation and galvanising public opinion over global warming.
Mr Huhne, the party's environment spokesman, called for members to " raise our sights and our goals" and insisted the Liberal Democrats were near "tipping point". He said the public would turn to the Liberal Democrats as the party of the environment because it is "in our gene pool".
Mr Huhne, who also said the party needed to re-engage the public in politics, said Sir Menzies needed the opportunity of a general election to project the party's distinctive politics.
He said: "Clearly I think we need to make sure the ideas we are putting across are the sort of ideas that really will rattle the cage."
Mr Huhne also urged the party's leadership to stress with voters the Liberal Democrats' strong track record in local government.
The Lib Dems boast that a record 1,600 delegates are in Brighton for the annual jamboree. But organisers have still had to shut off vast sections of the conference hall to hide the fact that they can't fill the cavernous venue
Ming 'not too old', say Zimmers
Sir Menzies Campbell won a vote of confidence in the face of sniping over his advanced years. It came from the music combo the Zimmers who were in Brighton last night for an Age Concern fringe meeting. John Tree, at 72 one of the younger members, said: "There is a culture of youth in everything and Ming has a difficult task, but I think he is doing very well."
Vladimir Putin is not the only one reviving espionage. The Conservatives have a top Cameron aide undercover in Brighton. "If I find any intelligence, I'll tell London straight away," the Tory agent said. Labour also has a friend from the Institute of Public Policy Research, a think-tank very close to No 10.
Double takes all round as the Ukip leader, Nigel Farage, scourge of all things from Brussels, happily wandered around the conference of Britain's most enthusiastic pro-European party. He was in town for a fringe meeting.
Vince Cable, the party's Treasury spokesman, who won widespread plaudits for predicting the banking crisis years in advance.
Ming Campbell, who admitted "gosh, I'm a failure" while swapping banter with radio comedienne Sandi Toksvig in a question and answer session. He said he was "scared stiff" before big speeches.
Fringe of the Day
The Independent's, naturally, where Chris Huhne and Nick Clegg went head to head. They are the two men most likely to slug it out for the leadership come the day that Sir Menzies steps down.
9am Debate on housing
9.40am Tax reform debate
11am Speech by health spokesman Norman Lamb
11.30am Immigration debate 2.30pm Speech by Michael Moore on foreign affairs