Tony Blair today sought to end the leaks damaging Labour's re-election campaign by publishing in full the legal advice that he was given before the Iraq war.

The Prime Minister, supported by Gordon Brown at a lengthy press conference dominated by the Iraq issue, said that he was ordering the publication of the 13-page memo from Lord Goldsmith, the Attorney-General, to show that he had nothing to hide from voters.

"The so-called smoking gun has turned out to be a damp squib," he declared.

But, with only a week to go until polling day, opposition parties refused to let sleeping dogs lie. Michael Howard abandoned a Conservative education manifesto launch to focus entirely whether Mr Blair had lied to the country over the legality of the Iraq war.

He said: "There is no more serious or grave decision for a Prime Minister to take the country to war. You have to be straight with the people, you have to tell the truth. I don’t believe Mr Blair did so."

After Channel 4 News yesterday published the six key paragraphs of Lord Goldsmith's advice, Mr Blair ordered that the whole memo be posted on the official Downing Street website. The Government had until now always refused to release the advice, claiming that it was covered by lawyer-client confidentiality.

The memo was sent to Mr Blair on March 7, 2003, as Jack Straw, the Foreign Secretary, was arguing for a UN Security Council resolution giving explicit approval to a US-led invasion. That plan was scuppered a few days later when France, a permanent member of the council, threatened to veto it.

The memo showed that Lord Goldsmith had major doubts about the legality of an invasion, but an argument could be made that it was legal. But he warned that failure to push a resolution through the Security Council would make that argument difficult to sustain.

He also warned that the Government would not necessarily be able to defeat any legal challenge to the war. "There are a number of ways in which the opponents of military action might seek to bring a legal case, internationally or domestically, against the UK, members of the Government, or UK military personnel," he wrote. "We cannot be certain that they would not succeed."

There has been no explanation, however, as to why the Attorney-General had changed his mind quite so drastically when he told Cabinet ten days later - on the eve of a crucial vote in Parliament - that the war would be legal because of an accumulation of previous Security Council resolutions demanding that Iraq disarm or face the consequences.

The issue eclipsed the launch of Labour’s business manifesto at the London headquarters of the financial information group Bloomberg in London today.

Under relentless questioning from journalists, Mr Blair said that he had taken the decision to make the full report public because it was already being circulated. He accused the opposition parties of "sheer opportunism".

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