The Foreign Office has been accused of attempting to cover up allegations by a senior government lawyer that Lord Goldsmith, the attorney general, changed his mind over the legality of the Iraq war.

In publishing a resignation letter written by Elizabeth Wilmhurst, a Foreign Office lawyer who resigned over the war, the government deleted a section alleging the attorney general had changed his view twice.

Responding, opposition MPs have demanded that Tony Blair make a statement to parliament.

Menzies Campbell, Liberal Democrat foreign affairs spokesman, said: "It's high time the prime minister came to the Commons.

"A full account of the attorney general's reasoning and how it evolved is essential."

A Foreign Office official said two sentences were removed from the document because their content related to the provision of legal advice in relation to the use of force against Iraq.