Mr Blair wants to bring down the curtain on his time in high office in the place where he began his fight to succeed John Smith and create the New Labour electoral success story.

He will inform the cabinet this morning before flying to his Sedgefield constituency to announce his decision at noon amid the party workers who first selected him as their parliamentary candidate on May 20 1983 at the age of 30. He is expected to make a personal speech that will insist he is a product of Labour and that his government has left Britain stronger than he found it.

Mr Blair will not quit as prime minister until the beginning of July, giving the party seven weeks to conduct its contests for leader and deputy leader. He will spend the intervening period seeking international deals on climate change, a new slimmed-down treaty for the European Union and extra cash for Africa.

With David Cameron branding Labour as "a government of the living dead" yesterday, Mr Blair will attempt to counter criticism that he is a lame duck by travelling to France tomorrow to meet the new French president-in-waiting, Nicolas Sarkozy, and then flying next week to Washington for talks with George Bush on climate change and Iraq, the two issues that have dominated their relationship.

He will also press ahead with announcements on academy schools, planning and energy supply. Two bills on criminal justice and terror will be published. Two policy papers, including one on the future role of the state, will be published on Monday.

Mr Brown is planning to launch his campaign to succeed Mr Blair tomorrow, giving the country the first glimpse of the prospectus the next prime minister will offer the country over what is expected to be at least two years in No 10. He is expected to offer broad themes, rather than a string of rabbit-out-of-the-hat policies.

One of Mr Brown's closest advisers, Ed Miliband, praised Mr Blair's legacy at an event held last night by the Progress thinktank in London, but he acknowledged Labour had to do more to end child poverty and win the argument about tackling crime and the causes of crime. He also urged the party to offer "a clear ethos of equality, community and empowerment".

Lord Giddens, the "third way" guru, urged Mr Brown to make a significant early speech on foreign policy which acknowledged the mistakes in Iraq and promoted a multilateral foreign policy.

Although some have criticised Mr Brown's silence about his intentions, one cabinet member said yesterday the chancellor's reticence has built up expectations perfectly. His campaign team is thought to have nominations from at least 250 Labour MPs, 205 more than he needs to get on to the ballot paper.

The two leftwingers still hoping to mount a token challenge to Mr Brown for the leadership - Michael Meacher and John McDonnell - will meet today to see who has gathered more nominations. Mr Meacher is claiming 24 supporters. Mr McDonnell has not disclosed the number of MPs backing him, but his supporters have cast doubt on the firmness of Mr Meacher's numbers.

The two have agreed to hold a press conference this afternoon announcing which of them will go forward as the candidate of the left. There is no guarantee that either can secure the 45 nominations required to prevent Mr Brown being elected unopposed.

Mr Meacher believes that if he can get on to the ballot paper he can win a third of the electoral college, made up equally of MPs, the 180,000 party members and 3 million party affiliates.

It is expected that Mr Blair's deputy, John Prescott, will also announce his resignation before the Labour national executive meets on Sunday to set the precise timetable for the contest for the two posts, culminating in a meeting of the electoral college on June 30.

In a taste of the Tory attack to come Alan Duncan, the shadow industry secretary, said yesterday that while Mr Brown would get a popularity "bounce" when he takes over No 10 from Mr Blair his leadership would generate "nastiness in spades" against the Conservatives.

"No 10 will now be occupied by the wrong end of the pantomime horse," he said. Whereas Mr Blair had been hard to dislike, Mr Brown would not be and he would be aggressive. "We have tried to take the Punch and Judy out of politics. Under Gordon Brown it will be all Punch." Since 1997 Mr Blair had been "the great actor, but Gordon has been the playwright and director," Mr Duncan said.