The stalking spectre of black-hearted deceit should have hung heavily over this week's prime minister's questions. Instead, Gordon Brown's fumble brought the House down.

By Alex Stevenson

All the ingredients were there. In the build-up we'd seen David Cameron claim there was a "thread of dishonesty" running through the government. Then Peter Mandelson came out fighting this morning, accusing George Osborne of a "deliberate untruth". This PMQs was always going to be about one thing - who can be believed on public spending.

That's where the statistics come in. Having slain the capital spending dragon last week, Brown-killer Cameron moved on to bigger, brighter things - total spending.
We were just getting started when the disaster struck. Brown, unthinking perhaps, boasted of a "zero per cent rise in 2013".

For the briefest of moments the entire Commons froze. In cartoon-mode Wile E. Coyote Brown looks at the camera, lips trembling and eyes bulging, as he realises he's just walked off a cliff. He pedals against thin air. He flaps his arms desperately. But then it's too late, the zero per cent rise has condemned his PMQs to ignominy, and he plunges away into the ether.

It didn't quite happen like that, of course. But the stunned, embarrassed faces of the Labour backbenchers as the Tories yelled and jeered said it all. "I think that answer gets zero per cent," Cameron observed, to predictable laughter.

It was all over before it had even started, but they pressed on nonetheless. Inevitably the issue became one of Brown's character. "Why can't he admit to the truth?" Cameron asked. Later he referred to the prime minister's "deceit". He wanted to know whether Brown could be "straight with the British public".

Nick Clegg added his own voice to proceedings, saying the "bogus debate" about public spending meant very little. How could he possibly trump the Brown-Cameron hate-fest? By hating them both himself! They were "both deliberately choosing to trade insults, so they can both deliberately avoid telling the truth", he said. If only someone would pay Clegg the courtesy of insulting him he might feel a little better.

Brown's response to all this was a muted disgust, a wobbling against "cheap jibes". He sought to stick to the politics. "I've already said, capital expenditure will riiiise," he quavered desperately. There were some decent points scored as he painted the Tories as the "party of unemployment". But the only real party being had in the Commons this lunchtime was on the benches behind Cameron.

It was "one of the most feeble performances" Brown had ever given, the Tory leader said. He was not in complete command - his claim that the Tory ten per cent cuts line was "not doing any damage to us" suggested he was a little rattled by that line of attack - but the vulnerabilities probingly sought by Brown were blown away by another classic prime ministerial gaffe.

Confronted with a serious, escalating row over dishonesty at the top of government, the prime minister turned this week's clash into yet another childish embarrassment. What was that puff of smoke, down there in the canyon of failed prime ministers? Ah yes, it was Coyote Brown, meeting reality with a bump.