Ministers 'hid true cost of Olympics'

They show the Government knew the 2012 Games would cost £1billion more than the bid claimed.

The revelation puts further pressure on Culture Secretary Tessa Jowell, who has been accused of massively under-estimating the burden on taxpayers.

But the Conservatives also blamed Gordon Brown for the cover-up as he has pledged to act as "ultimate guarantor" of all costs.

The first estimate for staging the Games was £2.4billion. When the bid was submitted to Olympic officials in late 2004, the budget had risen to £3.4billion.

Yet two months earlier, ministerial aides had been warned by accountants that the real bill would be a £1billion higher than that.

London was awarded the Games in July 2005, when it was assumed the cost would be £3.4billion as estimated.

But minutes of a meeting in November that year, attended by Treasury officials and accountants, confirm ministerial aides had been warned of the extra bill a year earlier.

The latest budget for staging the Games is £9.3billion.

Shadow Chancellor George Osborne said: "It turns out that Gordon Brown knew all along that the published Olympic budget was wrong, and he's spent the last year trying to cover his tracks."

A spokesman for the Department of Culture, Media and Sport said: "It is nonsense to suggest we are being anything other than as open as possible on Olympic costs.

"Responsibility for the costs of the Olympics are a matter for the department, not the Treasury."