The attorney general, Lord Goldsmith, warned less than two weeks before the invasion of Iraq that military action could be ruled illegal.

The government was so concerned that it might be prosecuted it set up a team of lawyers to prepare for legal action in an international court.

And a parliamentary answer issued days before the war in the name of Lord Goldsmith – but presented by ministers as his official opinion before the crucial Commons vote – was drawn up in Downing Street, not in the attorney general’s chambers.

This shouldn’t play well for Mr Blair, but it probably won’t make much difference in the long run. Nobody trusts what he has to say over Iraq, and facts like these shouldn’t make much difference to the general election result.

Sir Menzies Campbell, the Liberal Democrat foreign affairs spokesman, said the government’s position had been seriously undermined. “The substance of the attorney general’s advice, and the process by which it was partially published, simply do not stand up to scrutiny,” he said.

Sir Menzies added: “The issue is all the more serious since the government motion passed by the House of Commons on March 18 2003, endorsing military action against Iraq, was expressly based on that advice.”

He continued: “The public interest, which the government claims justifies non-publication of the whole of the advice, can only be served now by the fullest disclosure.”

I don’t really see how publishing the advice would serve the public interest, but I think that hiding it is against the public interest. So, in that sense, I think Mr Blair should come clean and publish the full advice. But he almost certainly won’t.