Robin Cook became the first member of Tony Blair's cabinet to resign in protest at the impending conflict with Iraq.

With today's papers speculating that Clare Short, the international development secretary, may join him on the backbenchers, the former leader of the Commons said that Britain was embarking on a military adventure without international support.

Cook, whose resignation statement in the Commons chamber was greeted by a standing ovation by many Labour MPs, said that he did not believe that Saddam still had weapons of mass destruction and warned that he would be voting against military action at the end of the debate on the conflict tonight.

"Neither the international community nor the British public are persuaded that there is an urgent and compelling reason for this action in Iraq," he said.

"I cannot support a war without international agreement or domestic support."

Today's Guardian speculates that either Hilary Armstrong, the current chief whip, or Jack Cunningham, the former "cabinet enforcer" are in the frame to succeed him as leader of the House.