TONY BLAIR is to endorse Gordon Brown as his successor as prime minister after he officially announces next week his intention to resign.

The prime minister, who will fire the starting gun on the leadership race on May 9 or 10, made his decision in the past few days after David Miliband made clear he would not be challenging Brown for the premiership.

Blair will support Brown, his long-time friend and foe, even if Charles Clarke or John Reid decides to embark on a “kamikaze” mission to prevent the chancellor having a smooth coronation. Brown will face a challenge anyway from a left-wing MP, either Michael Meacher or John McDonnell.

“If David Miliband had stood it would have led to a real dilemma for Tony,” said a Downing Street insider. “Miliband standing aside has made it easy for Tony to endorse Gordon. He will do that now, but couldn’t have done if David had stood.”

Blair has been encouraged by Brown’s open support for his six policy reviews, which the prime minister set in motion last year to ensure that his reforming legacy would endure.

The prime minister will make his position clear when Brown officially launches his campaign, which is likely to be within a few days of Blair’s announcement of his timetable for leaving office. After a seven-week leadership and deputy leadership contest, Brown is set to take over in the first few days of July.

For several years Blair has refused to endorse Brown unequivocally, although he has hinted he would like to see the “big clunking fist” of the chancellor smash the Tories at the next general election.

This weekend Tessa Jowell, the culture minister and key Blairite, will publicly back Brown, although it has been widely believed that she will lose her job under the new regime.

However, just as Brown prepares to take over, some insiders who have spent time with him in the past fortnight report that he is “depressed” about his electoral prospects, particularly in the south of England and among middle-class voters. Blair recently tried to encourage him, but his help was not welcomed by Brown.

A YouGov poll published on Friday gave David Cameron’s Tories a 10-point lead over a Brown-led Labour government. In this week’s local council elections, Labour is expected to fall to its worst showing in local government for more than 50 years.

While the chancellor recognises that he is still popular in Scotland, he considers the corollary may be that he is “unpopular” in England.

He is also said to be worried about the impending publication of the Downing Street diaries of Alastair Campbell, Blair’s former communications director, even though they have been heavily edited so as not to cause trouble for Brown and Labour. Campbell was witness to many meetings between Blair and Brown, some of which ended acrimoniously.

“Gordon is possessed by thoughts that he must reinvent himself,” said one insider. “He has already tried to make himself more ‘human’ to the public but it does not appear to be working, if you look at the polls. Others are advising him just to be himself.”

In an ITV television interview today, the chancellor does not deny suggestions he has been damaged by the prime minister remaining in office for so long.

Blair’s wife Cherie is said to want her husband to continue in office until mid-July, when the school holidays begin. This would give Brown’s supporters just days to make an impact at Westminster before parliament shuts for the summer recess.

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