Nick Clegg's pledge to stand for the Liberal Democrat leadership whenever Sir Menzies Campbell steps down was branded "premature" by a senior colleague today.
The party's environment spokesman, Chris Huhne - who, along with Mr Clegg, is most often tipped as a future Lib Dem leader - said there was no vacancy to discuss.
"There is no vacancy, and it would be premature to even talk about the position of there being a vacancy," he told journalists.
"I'm not the kind of Michael Heseltine figure who plans their route to Downing Street from the day they came out of nappies. I wait for opportunities and then decide at the time."
His comments come after Mr Clegg, the home affairs spokesman, last night told an Observer fringe event that he would stand for the leadership whenever Sir Menzies stepped down.
However, the former MEP and rising star within the party denied suggestions there had been a deal between himself and the leader.
The denial followed claims in yesterday's Mail that Mr Clegg agreed not to stand against Sir Menzies when Charles Kennedy was forced to quit in January last year, in return for his backing when he finally stands down.
Speaking at the Observer fringe meeting with Andrew Rawnsley at the party conference in Brighton, Mr Clegg branded the suggestion "rubbish".
"If you are asking me would I stand against Ming, the answer is no," he said. "If you are asking me would I throw my hat in the ring if there was vacancy in the future, I probably would - but my crystal ball is no clearer than yours.
"You have to sometimes hold your nerve. At a time when Sir Menzies is being attacked with barely disguised ageism... the only response is to pull together, put up two fingers and say don't you dare push us around."
The Lib Dem leader's chief of staff, Ed Davey, today denied that Mr Clegg's statement of ambition was damaging to the party leadership, saying: "We've made very clear there is no vacancy, and Ming has made very clear he is leading us into the next election and beyond."
The party has been struggling - with little success - to escape criticism of Sir Menzies' "disappointing" performance and turn the spotlight onto policy.
However, there was a boost for the Lib Dems today when an ICM/Guardian poll put the party on 20% - up two points from last month.
At another fringe meeting last night, a frustrated Mr Clegg suggested that he and the rest of the Liberal Democrat shadow team should stand back and allow Sir Menzies to present policy.
"Ming should have been less generous to people like me and David [Laws]," he told an IPPR debate on liberalism. "Everything should have gone via Ming. Maybe that's what we should do in the run-up to the general election."
The home affairs spokesman said the national print media had "the psychology of the playground bully" and the Liberal Democrats would do better to concentrate their efforts on local radio, where "people believe what they hear".