The Speaker of the House of Commons intervened and asked the prime minister to withdraw a reference to shadow chancellor Ed Balls as a "muttering idiot".

David Cameron was answering a question from a Liberal Democrat MP when he appeared to become irritated by off-camera taunts from Mr Balls.

After much cheering and jeering from a raucous Commons, the PM agreed to withdraw his barb, saying he would instead describe Mr Balls as "the man who left us this enormous deficit and this financial crisis".