Campbell will quit before conference

Alastair Campbell will announce his departure from Downing Street no later than Labour's party conference, which begins on 28 September, it was said today.

The Prime Minister's much-criticised communications director plans to wait until the Commons intelligence and security committee reports in mid-September on the charge that he "sexed up" last year's intelligence dossier on Iraqi weapons of mass destruction.

Mr Campbell is confident the report will clear him of the allegations, levelled by the BBC, opening the way for him to go with honour.

Today it was revealed that Mr Campbell was on the point of quitting three months ago. He told Tony Blair on 7 April - while they awaited a visit to Belfast by George Bush - that he wanted to step down, and on 28 May is said to have drafted a press release announcing his departure.

The very next day, however, the BBC broadcast its report claiming that Downing Street had tampered with the dossier, triggering the row that has raged ever since.

Mr Campbell, furious at what he believed was an attack on the integrity of the entire Government, himself included, has told friends he will not be hounded out but will "go at a time of his own and his family's choosing". It now looks all but certain he will depart at about the same time as his partner, Fiona Millar, who is due to step down in the autumn as aide to Cherie Blair.

The exit strategy still carries considerable risks for Mr Campbell. Even if the Commons committee clears him, as he expects, there is the danger that he could be heavily criticised as a result of the inquiry carried out by a senior judge, Lord Hutton, into the death of weapons expert David Kelly.

A key part of the investigation will be what role, if any, Mr Campbell played in the events leading up to the exposure of Dr Kelly as the mole who tipped off the BBC.

Mr Campbell's going will deprive Mr Blair of one of his closest and most long-standing advisers, ushering Downing Street into uncharted territory. This party conference will be his tenth as Mr Blair's press chief.

But No10 has already launched an operation to prepare for the exit, leaking late yesterday the fact that Mr Campbell had held talks about his future with Mr Blair.

The operation, itself a classic piece of spin, appeared designed to demonstrate he would go at a time of his choosing.

The news brought mixed reactions this afternoon from critics and allies. One senior Labour backbencher, MP Ian Gibson, said: "I am aware the Prime Minister will miss his guidance, but the show must go on." He suggested Mr Campbell's departure would lead to "a more listening, less aggressive style which might be to the party's advantage".

Culture Secretary Tessa Jowell, one of the few surviving Blairites in the Cabinet, leapt to Mr Campbell's defence.

She declared that he was "a person of extraordinary talent who has been a force for great good in the Government and who is absolutely rooted in Labour values". Ms Jowell, speaking on the BBC's World At One, acknowledged that the Government had too often become locked into a "Westminster-centric debate that has very little to do with the lives of people."

And while defending Mr Campbell she said she accepted that politicians should steer clear of "the macho engagement, somebody has to win, somebody has to lose" approach which did not match the realities of a complex political world. Ms Jowell herself, however, earlier upped the stakes in the continuing tussle with the broadcasters. She warned that the BBC must show it is "worthy" of public trust.

And she confirmed the Government will embark on a radical and wideranging review" this autumn about the renewal of the BBC's charter in 2006.

Ms Jowell made clear the inquiry into events leading up to the death of Dr Kelly will have a bearing on the "scope of the review".

The Culture Secretary delivered her warning in an interview with The Times, one of the newspapers most sympathetic to Downing Street and most hostile to the BBC in the dispute over the dossier.

Ms Jowell was careful not to issue any direct threat. She said that the review of the BBC's future, including whether supervision should be taken out of the hands of the Governors and handed to the independent watchdog Ofcom, was "quite separate" from the Hutton Inquiry into the death of Dr Kelly.

However, she went on: "I will consider very carefully any recommendations and conclusions which can be drawn from the Hutton Inquiry in relation to the BBC."

The recent damage done to the Government was highlighted by an opinion poll today. The poll, by YouGov for the Daily Telegraph, found more than six out of 10 voters believed the Government appeared to have "lost control and be at the mercy of events."

Almost half, 47 per cent, said they did not believe a word Mr Blair said, and no fewer than 68 per cent said they believed there was "a culture of deceit and spin at the heart of the Government".

The poll also showed the Conservatives at 37 per cent, against 34 for Labour and 22 for the Liberal Democrats.