Tony Blair will defend himself in a Commons debate next week against charges that he misled the public in the way he presented intelligence before the Iraq war.

The prime minister agreed to a demand from Michael Howard that he should appear in a planned debate on Iraq.

The original plan had been for foreign secretary Jack Straw to lead for the government, and for Michael Ancram to speak for the Conservatives.

On Thursday, Howard directly accused Blair of misleading the public over the Iraq intelligence.

"When you have such a contrast, such a yawning gap, between the words used by the prime minister and the actual intelligence on which his words were meant to be based, then there is a very legitimate question to be asked," he told BBC Radio 2.

Meanwhile, Britain’s intelligence machinery is facing a major review, following Butler's strong criticisms of MI6.

Sir David Omand, the head of the Cabinet Office, is producing an action plan that could lead to changes affecting the whole of the intelligence community, Whitehall sources said.

A new chairman of the Joint Intelligence Committee is expected to be announced, possibly next week.

Liberal Democrat foreign affairs spokesman Sir Menzies Campbell called yesterday for the new chairman to be someone of the stature of Sir Jeremy Greenstock, who retired recently as the prime minister’s special envoy in Baghdad and was ambassador to the UN.

John Scarlett, the intelligence chief accused of becoming too close to Downing Street in the approach to the Iraq war, remains under pressure to withdraw as the next head of MI6.

The Telegraph says that Sir Richard Dearlove, the outgoing chief of MI6, opposed him as his successor.

He backed Nigel Inkster, his vice-chief, instead.