Michael Howard, the Tory leader, said today that Tony Blair had failed to ask fundamental questions about intelligence on Iraq's weapons of mass destruction and should resign.

The Prime Minister admitted yesterday that he had asked the Commons to approve the war against Iraq without knowing that the 45-minute claim in the Downing Street dossier referred only to battlefield weapons.

Geoff Hoon, the Defence Secretary, and Robin Cook, the former Foreign Secretary, were aware at the time that the claim did not refer to long-range weapons, but Mr Blair was not.

Mr Howard said today: "I am accepting what the Prime Minister told us at face value. He said he never knew, he never bothered to ask this question.

"If I were Prime Minister and I had failed to ask that basic question before committing our country to war I would be seriously considering my position."

Margaret Beckett, the Environment Secretary, dismissed Mr Howard’s attack as“nit-picking of the highest order”.

“To use it to say ‘Oh the Prime Minister should resign’ - do you suppose Winston Churchill went round asking precisely the kind of munition they had in the Second World War and would that have been a valuable use of his time?” she said on BBC Radio 4’s PM programme.

Downing Street disclosed tonight that Mr Blair did not discover that the 45-minute point referred to battlefield weapons until after the war when the Parliamentary Intelligence and Security Committee launched its inquiry.

The Prime Minister’s official spokesman stressed that it did not affect the statements elsewhere in the dossier that Saddam Hussein had long range missiles capable of carrying chemical and biological warheads.

“The Government’s belief, the Prime Minister’s belief, was that Saddam had a WMD capability and that that capability was both battlefield and long-range,” the spokesman said.

“The long-range issue doesn’t rest on the 45 minute point.”

Mr Hoon faced a grilling by MPs today over the dossier row after he sought to play down the controversy today in a round of broadcast interviews.

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