PMQs sketch: Ed ‘muttering idiot’ Balls is a maestro of irritation

However much David Cameron may swat at the Balls bluebottle, he will never be able to squash the superbly annoying shadow chancellor.

Ed Balls is not supposed to play a big part in prime minister's questions. This session is supposed to be about Cameron asking questions from Ed Miliband and other MPs, and nothing whatsoever to do with opposition frontbenchers.

Yet such is Balls' capacity for winding up the prime minister that he has succeeded in getting a rise out of Cameron for the second time in six months.

It is the consistency of the shadow chancellor's drip-drip approach that proves so infuriating. If someone tapped you with a pencil on the shoulder for half an hour you would probably end up punching them in the face. Balls deploys the political equivalent every PMQs.

His excellent technique is composed of a combination of hand gestures and barbed comments which are barely audible above the throng. In this respect his tactics are not dissimilar to those frequently employed by boorish males in nightclubs.

Like clubbers, Balls has a few stock gestures which he brings out time and again. He knows they get results. His favourite hand movement is the 'flatliner'. Palms down, fingers together, Balls moves one hand to and fro to indicate a graph reflecting the UK's stagnant economy. When he gets bored of this he moves on to the 'calm down dear', a hushing sort of motion patting an invisible prime minister in front of him on the head.

These are always useful contributions to Labour's cause, but they were not the primary reasons for Ed Miliband's victory over Cameron in the main exchanges today. The Labour leader was very effective in contrasting No 10 adviser Adrian Beecroft's desire to give companies the right to sack employees willy-nilly with the views of Lib Dem business secretary Vince Cable, who thinks the idea is "bonkers".

Cameron tried to counter by raising the trade unions' grip on Labour, but its relevance was limited at best. Miliband, uncharacteristically going off script, neatly blocked the riposte by pointing to "Tory millionaire donors". 2-1 to Miliband, I'd say.

It was a rowdy session, partly because Balls was virtually never silent, but mostly because PMQs these days is a more combative and more even sort of contest. Miliband knows the momentum is shifting his way, and has taken to openly grinning at Conservative MPs when he is being barracked. His gleeful complacency is rather off-putting to government MPs, who prefer their Labour leaders in the Gordon Brown mode – downcast and glum. Seeing Miliband openly laughing at Cameron throughout the prime minister's last answer might have put them off their lunch.

It would have done had Cameron not made sure they did not go away empty-handed. Not that the snap, when it came, was prejudged. The PM was in the middle of delivering a very boring answer to a very boringly loyal question from Stephen Williams, the Liberal Democrat MP. Cameron was talking about the need for fiscal credibility, and combining that with an active monetary policy, and structural reforms to make us competitive… blah, blah, blah. At this point my eye had fallen on Balls, who was once again rabbiting across the chamber to Cameron.

The PM, a hard look in his eye, finished his long list of coalition achievements with an unexpected flourish. He wanted ministers to continue coming up with "innovative ways of using our hard-won credibility which we wouldn't have if we listened to the MUTTERING IDIOT sitting opposite me…"

The Commons erupted. Tory backbenchers, forgetting their leader's defeat in the main exchanges, cheered alongside the Liberal Democrats. "More!" they bayed, not bothering to hide their acclaim for their pugnacious leader. Cameron could have been the popular school bully in the playground, not a party leader and prime minister.

Balls, his grin now frozen on his face, moved forwards and backwards in his seat. Speaker John Bercow, who had kept quiet during Miliband's six questions, now had no choice but to interrupt. He demanded that Cameron take back the "idiot" slur, as it was thoroughly unparliamentary. "A simple withdrawal will suffice," Bercow stated. Even then Cameron could not resist getting in another jab. "I will replace it," he declared, with 'the man who caused this enormous deficit'."

Balls looked a little sheepish even after the kerfuffle had died down. He received some wise words of advice from shadow business secretary Chuka Umunna, to which he kept his lips pursed and shook his head.

But his momentary embarrassment was unnecessary, for Cameron lashing out at him was a success for his party. It makes the PM look unpleasant. That is the prize for Balls' limitless supply of irritation, which once again saw him steal the show this lunchtime. As regular nightclub attendees will attest, often the most annoying males present get the best results.