Tony Blair admitted that his announcement he will quit as Prime Minister this year has created a period of "uncertainty" for the Government.
But he insisted that he would have faced "a load of different problems" if he had kept quiet about his intentions.
And he made clear he did not want to repeat the fate of Margaret Thatcher, who said she would go on and on, but was then "absolutely belted and chucked out" by her own party.
In an interview with The Observer, Mr Blair suggested that his departure would draw the sting of the Iraq War - possibly allowing Labour to win back voters who have deserted it because of his decision to join US-led military action.
Referring back to the 2005 election, he said: "Iraq was a factor then. In a sense, when I go, that goes with me."
Mr Blair played down suggestions that his successor - widely expected to be Chancellor Gordon Brown - would have to call a snap election to earn his own mandate as PM, saying he expected it to be "a significant time" before the poll was called.
He declined to offer a fresh endorsement of Mr Brown as his successor, referring instead to the "myriad of complimentary things I have said in the past" about him.
And he refused to rule out the possibility that David Cameron's Conservatives would win the coming General Election, saying only that Labour should not be "fearful" of the reinvigorated opposition, but say: "Right, we're in a fight, so let's see who's got the best policies and agendas - Across a range of issues, we do."
Mr Blair said that the process of choosing a new leader while in Government would be "a test of maturity" for the Labour Party.
But he rejected suggestions that the launch of a website to debate future Labour policy by Blairite former ministers Charles Clarke and Alan Milburn would stir up trouble for the party, insisting that the public would not mind a "sensible debate about the future".
