David Cameron was forced to withdraw angry remarks made towards Ed Balls in the House of Commons on Wednesday afternoon after he called the shadow chancellor a "muttering idiot".
Balls spends much of prime minister's questions trying to wind up the prime minister by heckling him from across the chamber and making hand gestures.
It appeared to succeed today, as Cameron responded to a question about his approach to the economy.
He told the Commons that the coalition had secured: "hard-won credibility which we wouldn't have if we listend to the muttering idiot sat opposite me".
His comments came after Balls reportedly wound up Cameron throughout the session by asking him how many glasses of wine he had drunk this morning.
It has been claimed that the prime minister likes to relax on a weekend by playing games on his iPad and drinking several glasses of wine at lunch.
Cameron's remark prompted uproar in the House of Commons from all sides and the prime minister was forced to withdraw it - or at least half of it.
The Speaker told Cameron: "Please withdraw the word 'idiot', it's unparliamentary".
Cameron responded: "I will replace it with 'the man who left us this enormous deficit and financial crisis."
Following the confrontation Balls took to Twitter to explain what he had been saying: "For the record, I was simpy asking the prime minister, as he boasted the economy was on track: 'Tell us about the recession..'"
It is not the first time the prime minister has lashed out during prime minister's questions and Labour pursue a direct strategy to try and wind him up.
Last week Ed Miliband noted has gained something of a reputation for having a bad temper and offered him a piece of advice.
"I know he is going to have extensive training before he goes before Leveson, I've got a suggestion, I think it should include anger management," he said.