Faced with such doubts from the military, Britain's Attorney General Lord Peter Goldsmith hastily redrafted "prevaricating" advice to the government just days before war was launched last March, to assure the armed forces the conflict would not be illegal, the Observer reported.

Short, who earlier this week controversially claimed that London spied on UN Secretary General Kofi Annan during the tense weeks leading to the invasion of Iraq, told the paper:

"I was told at the highest level ... that the military were saying they wouldn't go (to war), whatever the PM said without the attorney general's advice.

"The question is was the AG (attorney general) leant on?"

Short, Britain's former international development secretary, quit in May in protest over the Iraq invasion.

Earlier this week, she sparked controversy by alleging that transcripts of Annan's bugged telephone calls were circulated to senior British ministers.

Her claims came after British prosecutors dropped charges against an intelligence translator, Katharine Gun, who leaked a memo revealing apparent US and British plans to spy on members of the UN Security Council in the run-up to the conflict.

While Tony Blair attacked Short's revelation as "deeply irresponsible", the opposition demanded that the prime minister say directly whether she was telling the truth or not.

Blair also came under pressure to reveal the legal reasoning for joining the invasion of Iraq alongside the United States.