Blair faces pressure over Butler

Tony Blair's hopes of drawing a line under the Iraq weapons row were dashed today when MPs took the first steps to re-open the affair.

Claims that MI6 and Whitehall chiefs embarked on a cover-up to protect Mr Blair are also expected to be probed.

The intelligence and security committee, two of whose members sat on the Butler Inquiry, may re-interview Joint Intelligence Committee chairman John Scarlett, MI6 chief Sir Richard Dearlove and Mr Blair's personal intelligence adviser, Sir David Omand. Lord Butler stunned Westminster last week when he revealed that MI6 had serious doubts about the three Iraqi informants behind the Government's most important claims on Saddam's weapons arsenal.

Crucially, the spies agency had withdrawn a report claiming that Iraq was continuing to produce chemical weapons. Further checking after the war found that the source for it was unreliable and the intelligence itself "unsafe".

Yet in giving evidence to Lord Hutton's inquiry last August, neither Mr Scarlett nor Sir Richard Dearlove revealed that the intelligence had been withdrawn a month earlier. Downing Street says that Mr Blair did not learn the intelligence had been discredited until earlier this year. MPs want to know if he was kept in the dark to protect him politically.

The foreign affairs committee was today beginning moves to re-examine what it was told by the Government on Iraq, reopening an investigation it concluded last year. The Labour-dominated committee then narrowly avoided censuring Downing Street - largely on the casting vote of its chairman, Donald Anderson.

But Labour MP Eric Illsley has told the Evening Standard he will today ask clerks to start comparing the evidence the committee received with evidence to the Butler Inquiry. If the committee finds there is a case to answer, Foreign Secretary Jack Straw will be recalled along with other key Foreign Office witnesses.

The fresh evidence may be taken when Parliament is recalled in September, ensuring the issue continues to dog Downing Street as the conference season approaches.

Sir David Omand is already set to be recalled by the intelligence and security committee to explain whether his role cuts out the Cabinet Secretary from intelligence matters.

But the committee may now also ask Sir David why he did not tell Mr Blair last summer that key intelligence had been declared "unsafe".