US, UK intelligence services both made mistakes: Cook

"It was a fundamental error that went wrong on both sides of sides of the Atlantic," Cook said.

"The governments had made up their minds that Saddam had weapons and must be a threat. They had made up their minds they were going to war.

"The intelligence agencies were then left in the position of finding intelligence to support the conclusion.

"It should have been the other way around: you look with intelligence and then build your policy on what you know."

However, he dismissed the idea put forward in the US Senate report that there had been a global failure of pre-war intelligence as "garbage".

"Nobody except Washington and London thought that Saddam was such a threat that we had immediately to go to war," he said.

Cook, who was foreign secretary from 1997 to 2001 and subsequently leader of the House in parliament, resigned in March 2003 because he disagreed with Prime Minister Tony Blair's decision to enter the US-led war on Iraq.

A commission of enquiry headed by Lord Butler, a top civil servant, is due to make public its findings on the process that led London to believe before the war that Iraq possessed Weapons of Mass Destruction (WMDs) on Wednesday.

Cook commented that "the prime minister needs a catharsis. He needs an opportunity and perhaps the Butler report will give him that, to say look, there were mistakes made but lessons have been learned and, above all, he needs to say it is not going to happen again.

"He has never in any way tried to walk away from the fact that the decision to go to war was a very personal one of his own and he fully accepts that responsibility," he added.