Lib Dem deputy leader Sir Menzies Campbell has said he has no intention of launching a leadership challenge against Charles Kennedy.
Sir Menzies has until now stayed silent about the leadership crisis
Sir Menzies has until now refused to say whether he backs his leader, who has come under fire from unnamed MPs.
But now he has issued a statement saying: "As long as Charles Kennedy remains leader of the Liberal Democrats he has my full support."
Mr Kennedy earlier said the party would be "thrusting" and "united" in 2006.
The Lib Dem leader came under fire from senior colleagues at a "shadow cabinet" meeting on Tuesday, with some privately saying he must improve or stand aside.
Sir Menzies met Mr Kennedy privately on Wednesday and afterwards did not answer journalists' questions about whether he supported his leader.
In his new statement, he says: "Unlike others I followed the advice of the chief whip and Mr Kennedy's own office not to comment on private conversations with him.
"I do not have any intention of standing against Charles Kennedy. I welcome the fact that Simon Hughes and Mark Oaten have given similar assurances.
"As long as Charles Kennedy remains leader of the Liberal Democrats he has my full support."
Sir Menzies, 64, was seen as a potential successor as leader, particularly as he has just been given a clean bill of health after treatment for cancer.
Another possible successor, party president Simon Hughes, has said he expects Mr Kennedy to stay in his job as "the overwhelming majority" of MPs want him to continue.
Mr Hughes, who was defeated by Mr Kennedy in the 1999 leadership election, told BBC Radio 4's Today programme that "concerns" had been raised in recent days but that Mr Kennedy should stay to contest the next election.
He said: "Menzies and all Charles' colleagues have had a chance to express their view to Charles privately."
'Getting on the front foot'
Speaking ahead of a visit to Brussels, Mr Kennedy said it was "a good day" for the party as "speaker after speaker" had backed him at a meeting of Lib Dem MPs on Wednesday night.
"We can look forward to a restful but creative recess now over Christmas and New Year and all come back united on the front foot in January," he said.
"I think people in British politics will be very pleased because they want a thirsting and thrusting Liberal Democrat party that's out there making our distinctive case - and that's what I'm getting on to do."
Later, he told Sky News: "In the top job, if you want to make an omelette, you've got to crack a few eggs."
When asked about Sir Menzies, Mr Kennedy added: "Your best friends are often your most frank friends."
He added that he was "not proposing any changes" to his senior colleagues. Sir Menzies was, in any case, elected as deputy leader rather than being appointed by Mr Kennedy.