Tony Blair should stand aside within a year and let Gordon Brown become prime minister, former Labour chancellor Lord Healey has told the BBC.
Lord Healey's comments will be an embarrassment for Tony Blair
He said that after nearly seven years at Number 10 Mr Blair was in danger of becoming "too fixed" and argued Mr Brown would do the job "very well".
Lord Healey, who was defence secretary as well as chancellor, said Mr Brown lacked Mr Blair's charisma.
But he added marriage and fatherhood had made him "start smiling".
Too long in the job?
"I hope that Tony will decide to retire from that job in the next year or so because I think that Gordon would do it very well," he told BBC News 24's My Politics.
"He hasn't got the charisma of Tony Blair but he does at least now start smiling because ever since he married Sarah, and it's particularly since they had a child, I think he smiles a great deal and he's a very attractive man, a very nice man."
"If you stay in the same job too long I think you tend to get too fixed in your manner of dealing with problems and it's time for a change in that sense and I think that Gordon would do it very well.
"The generation after that I don't really know them well enough to say anything."
Lord Healey added that he had known Mr Brown since he was a student.
The Labour grandee is no stranger to controversy previously likening debating with the then Tory chancellor Geoffrey Howe to being "savaged by a dead sheep".
He also accused Margaret Thatcher of "glorying in slaughter" during the 1982 Falklands conflict.
Lord Healey was a key figure under Harold Wilson serving as defence secretary for six years from 1964.
He went on to become chancellor from 1974 to 1979 both under Wilson and under James Callaghan.
His call won backing from Labour veteran Tam Dalyell, who said: "American Presidents have eight years at the most. Tony Blair has now had ten
years as leader of the party and been prime minister since 1997.
"That is enough for the Archangel Gabriel. And Mr Blair is not the Archangel
Mr Blair's official spokesman said it was not the first time Lord Healey had offered such advice and the prime minister was not focusing his energies on what ex-ministers were saying.
Lord Healey's interview with My Politics can be seen on BBC News 24 at 2145GMT on Saturday 6 March.