After his 2003 resignation from the Cabinet, Cook remained an active backbench Member of Parliament until his death. After leaving the Government, Cook was a leading analyst of the decision to go to war in Iraq, giving evidence to the Foreign Affairs Select Committee which was later relevant during the Hutton and Butler inquiries. He was sceptical of the proposals contained in the Government's Higher Education Bill, and abstained on its Second Reading. He also took strong positions in favour of both the proposed European Constitution, and the reform of the House of Lords to create a majority-elected second chamber, about which he said (while he was Leader of the Commons), "I do not see how House of Lords can be a democratic second Chamber if it is also an election-free zone".