Former prime minister Sir John Major has said that parliamentary reform is badly needed to restore trust in politics and has heavily criticised the decision to go to war in Iraq.

Speaking to the Today programme, which is being guest edited by Liberal Democrat peer Baroness Williams, Sir John said that changes needed to be put in place which reasserted the "independence of mind" of backbench MPs and remove special advisers practicing the "black arts".

Criticising Tony Blair's decision to go to war, he said he only supported the war because he had believed what the Prime Minister said about weapons of mass destruction. But he now had cause to doubt that belief.

"The suspicion arises that this was more about regime change than it was about weapons of mass destruction," he said.

"The then Prime Minister Tony Blair may have known things that I don't know which may make things that seem curious fully understandable.

"What I do think is not understandable - the argument that Saddam Hussein was a bad man and therefore must be removed simply won't do.

"There are many bad men around the world who run countries and we don't topple them."