A civil servant and an MP's researcher were today found guilty of breaching the Official Secrets Act after leaking an "extremely sensitive" four-page memo about confidential talks between Tony Blair and President Bush.

The document, which concerned the two leaders' strategy over Iraq, was passed by the Cabinet Office communications officer David Keogh, 50, to Leo O'Connor, who worked for the anti-war Labour MP Anthony Clarke in April 2004, in an attempt to portray the US President as a "madman" and influence the forthcoming US elections in favour of the then Democratic presidential candidate, John Kerry.

O'Connor, 44, placed it in Mr Clarke's constituency papers, but the Northampton South MP handed it to Downing Street and both men were arrested in the subsequent police investigation. Mr Blair later wrote to Mr Clarke personally thanking him for reporting the leak.

The memo came from a highly sensitive meeting at the Oval Office involving Mr Blair and Mr Bush to discuss political and military strategy over Iraq.

The summit is also believed to have featured Condoleezza Rice, then National Security Adviser, and Colin Powell, then Secretary of State, from the American side and Jonathan Powell, Mr Blair's chief of staff, who was assisting the Prime Minister.

The document's contents were so secret that much of the trial was held behind closed doors, and a large number of the memo's details could not be reported.

Giving evidence at London's Central Criminal Court, Keogh had said he felt strongly about the memo, which he had wanted to relay to diplomats overseas, and hoped it would come to wider attention.

"The main person in my mind was John Kerry, who at the time was American candidate for the U.S. presidential election in 2004," he had testified.

He admitted holding "unfavorable" views on President Bush, but pleaded not guilty to all charges, saying he did not think publishing the document would hurt Britain’s security or international relations.

John Farmer, defending O'Connor, said the war in Iraq was "the most controversial foreign affairs involvement of this country since Suez 50 years ago", however he insisted his client had no intention of passing the document on and fully expected his boss Mr Clarke to return it to Downing Street.

However, the prosecution alleged that British service personnel in Iraq could have faced attacks and increased danger had the document been made public, and the country's position could have been seriously damaged if it had been exposed.

As the jury found Keogh guilty of two offences and O’Connor guilty of one under the Official Secrets Act, the pair sat in the dock looking grim-faced.

The judge, Mr Justice Aikens, adjourned the court before sentencing while probation inquiries were made on behalf of O’Connor. He warned the jury not to repeat any of the secret information they had heard behind closed doors.

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