David Cameron: 'I last ate a pasty at Leeds station'. Source: Press Association Press Association

David Cameron's efforts to show he loves a hot takeaway far more than a private dinner with his rich backers came to a crumbly end when his fond memory of eating a large Cornish pasty at Leeds railway station turned out to be somewhat faulty.

The prime minister's problems began at the Treasury select committee on Tuesday when the fiercely independent and somewhat lugubrious Labour MP John Mann asked George Osborne why he was imposing VAT on hot foods such as pasties. He asked the chancellor when he had last eaten a pasty at Greggs the bakers.

Osborne – more interested in the dynamic modelling of tax reforms than hot food VAT anomalies – looked nonplussed, and said he could not recall. One tweet suggested he was then probably subjected to a Treasury presentation where he was told that pasties were "similar to mini boeufs en croute".

The Sun newspaper, currently intent on doing over the Tories, described him as the Marie Antoinette of the 21st century. Then Greggs chief executive Ken McMeikan denounced Osborne as out of touch, and warned hundreds of jobs were at stake if pasty prices were raised by 20%.

For Cameron's handlers, facing polls showing that two-thirds of the electorate once again regard the Conservatives as the party of the rich, this was more bad news in a week already filed under challenging. So when – in the middle of a Downing Street press conference on the Olympic legacy – the PM was asked about the treatment of pasties in the budget, he was primed to say how often he eats them.

He began to wax lyrical. "I think the last one I bought was from the West Cornwall Pasty Company. I seem to remember I was in Leeds station at the time and the choice was whether to have one of their small ones or one of their large ones. I have got a feeling I opted for the large one, and very good it was too."

But the West Cornwall Pasty Company outlet where he thought he enjoyed his last pasty closed two years ago. There was a Cornish Bakehouse booth at the station; that closed last week.

Despite U-turns on most things this week, Downing Street stuck to its line and insisted that the prime minister had eaten a pasty at Leeds station, but the date was unclear, and possibly the purveyors had not been West Cornwall Pasty Company.

This was just as well, since Gavin Williams, the ungrateful boss of David Cameron's favourite pasty-makers, was not interested in Cameron's endorsement of his product. He wanted "clarity and leadership" from the prime minister.

But clarity is a rare commodity in this area, since it seems a pasty can avoid VAT if it is served cold at the counter and then warmed elsewhere in the shop.

The Labour leader, Ed Miliband, not normally known for his proletarian manner, sensed he could save the squeezed middle. He rushed to a Greggs in Redditch – where he and Ed Balls ate sausage rolls – and announced that his party would make common cause with west country MPs and vote against the measure in the budget. Our middles may yet be unsqueezed.