Michael Howard, the Conservative leader, claimed that the prime minister has lost all credibility as a result of the Butler report.

While conceding that the intelligence services had "in many ways" got it wrong over Iraq's weaponry, their judgments included serious caveats, qualifications and cautions.

The Tory leader said that when Tony Blair presented his case to the country, he left these out.

"Their qualified judgments became your unqualified certainties. The question you must answer is why?" he said.

"I hope we will not face in this country another war in the foreseeable future but, if we did and Mr Blair identified the threat, would the country believe him?

"The question Mr Blair must ask himself is: Does he have any credibility left?"

Charles Kennedy, who refused to support the Butler inquiry, said that its conclusions indicated that the previous policy of containing Iraq was succeeding in preventing Saddam from developing weapons of mass destruction.

Blair also faced criticism from Robin Cook, who resigned from the Cabinet over of his opposition to the war, and Kenneth Clarke, the former Tory chancellor who suggested that he would not have secured a majority for military action if he had shown MPs the original intelligence.