As David Cameron spoke about the economy during Prime Minister's Questions, there was uproar in the Commons when he said people should not listen to the "muttering idiot" sitting opposite him.
The jibe was aimed at shadow chancellor Ed Balls.
The Speaker John Bercow interjected and called for order.
He then asked Mr Cameron to withdraw the word "idiot" which he said was "unparliamentary".
Mr Cameron said he was happy to withdraw the word - saying he would substitute it with "the person who left the UK with a huge deficit".
Shortly after the incident, Mr Balls tweeted: