John Rentoul: The fallacy that continues to dog Project Cameron

This was the flying pig manifesto, describing a Britain that will never be

"Bleating and babbling I fell on his neck with a scream." From the moment I heard that the Conservatives were launching their manifesto in Battersea power station, I could not get the lyrics from Pink Floyd's Animals out of my head. David Cameron said something about a building needing renovation symbolising the state of the country, in which case it was not clear what a temporary construction in the middle of a majestic ruin signified, as it was a run-down hulk for most of Margaret Thatcher's time, too. There is a carelessness about the past in Cameron that is curious for a Conservative. He did it again towards the end of the long morning's show. "The politicians have been treating the public like mugs for about 40 years," he said. At least it was a change from his usual "taking the public for fools", but he inadvertently trampled on Mrs Thatcher's period.

John Prescott said something about the flying pig, the blimp that Pink Floyd floated over the building for the Animals cover picture, right, although the obviousness of the attack from a rival politician rather deflated the joke. Yet there was an apt symbol. This was the flying pig manifesto, lighter than air and rhetorically describing a Britain that is never going to be. And the reason we know it is never going to be is because we have been promised it before. The Big Society? It is huge, inflated, fabricated, and mythical. It is about as meaningful as the "strong society" that Tony Blair used to talk about, which is not meaningless, just not real. The Big Society is full of meaning. It is that golden-glow yearning for a past that never was, which the artist who designed the cover of Labour's manifesto has sought to capture.

There was an unexpected echo of it in the video of Julie, the mother "voting for stronger families" in Llandudno, who had "never voted Tory before" but would do so this time in the hope of society going "back to where it used to be, when family was important and children were seen as a nice part of society". All I could hear was wave upon wave of demented avengers marching cheerfully out of obscurity into the dream.

The Conservative leader spoke from a text, which meant that parts of it were well crafted, but the overall effect was deadening. He is better when he is spontaneous. But I suddenly paid attention when he told me that something was "the answer to the question that people ask me the whole time wherever I go". Oh, no. There it was: the Answer, and I missed it. Because it turned out to be a question that had occurred to me, too. "How can you afford to make things better when everyone knows there is no money?" He would not tell us the answer again; all he would say was: "You're thinking about it in the wrong way. In the old way. In the Labour way."

What, is it old-fashioned or left-wing to think that a government's sums should add up? To all those people who think that cancelling £6bn of next year's rise in national insurance contributions, paid for out of a flying piggy bank called "efficiency savings", Cameron says: "You're thinking about it in the wrong way". We should be thinking: "With a deficit of £167bn, what's £6bn here or there?"

One member of the Shadow Cabinet was keen to talk to me about the "intellectual underpinnings" to the manifesto, but all I could hear was, "Dimly aware of a certain unease in the air... What do you get for pretending the danger's not real?"

My problem is that I understand the intellectual underpinning only too well. It is the old "small government, big society" fallacy that has dogged Project Cameron from the beginning. One of Cameron's best sound bites yesterday was: "It's not about 'You the government', it's about 'We the people'." Very Barack Obama. And I am as opposed to the nanny state as the next person. I do not like Gordon Brown's statist assumptions on the economy and public services. But the helium at the heart of the flying pig manifesto is the idea that if the Government stops doing stuff, people will organise themselves to fill the gap in ways that are equitable, fulfilling and tax-saving.

The manifesto has some good sections on schools and the environment. It didn't mention last week's smart device of limiting top pay in public-sector organisations to a multiple of 20 times the lowest paid. And the sections on health and social security are worse than useless. But its main weakness is its failure to answer the question that Cameron so rightly identified: how to pay for the "good government" that is going to replace "big government". The thing about really good government is that it is no cheaper than the big kind. Of course, no one expects much of manifestos, and it is a question that the Labour manifesto also fails to answer.

As Roger Waters sang, so long ago: "Ha ha, charade you are".

John Rentoul is chief political commentator for 'The Independent on Sunday'