Jack Straw’s decision to disregard advice from his top legal experts that war in Iraq would breach international law was yesterday branded “intolerable” by one of his predecessors as Foreign Secretary, Sir Malcolm Rifkind.

The inquiry into the conflict had heard yesterday that Tony Blair was warned two months before the invasion of Iraq that it would be illegal to go to war without United Nations’ authority, .

A slew of newly declassified Government papers showed Lord Goldsmith, then the attorney general, was initially “pessimistic” that there was sufficient legal basis for military action.

However, after being urged to change his view by the then foreign secretary Jack Straw – who warned against overly “dogmatic” legal advice – he eventually ruled it was lawful.

The inquiry heard how Mr Straw rejected the advice of his senior legal adviser at the Foreign Office, Sir Michael Wood, that an invasion without a UN Security Council resolution specifically authorising military action would be a “crime of aggression”.

Sir Michael’s deputy Elizabeth Wilmshurst, who resigned in protest on the eve of the invasion in March 2003, described the Government’s treatment of the legal advice as “lamentable”.

And Sir Malcolm said that Mr Straw should be put on the spot when he returns to the Chilcot Inquiry on February 8 .

A spokesman for Mr Straw said the Blackburn MP would not comment on the claims and expected him to address the issues at appearance before the inquiry in February.