He was asked about apparently conflicting remarks from Ken Livingstone, the Mayor, and Olympics Minister Tessa Jowell on the projected budget.

Jowell told a Committe of MPs on Tuesday the estimated £2.4375 billion bill for the Olympic Park had risen £900m.

Livingstone later told LBC Radio she had "made a mistake" because the budget would be reworked again by spring.

And while Jowell said her figures were separate from the costs associated with regenerating East London after the Games - Livingstone told the BBC that was were most of the increase would lie.

Theresa  May, the Conservatives chairman, said a statement was needed to "clarify the position and clear up the confusion", as the Mayor had said extra costs would be recouped after the Games.

She told MPs London's winning Olympic bid had been a wonderful coup which would leave a lasting legacy, but it was not an excuse for a "blank cheque", signed by Livingstone and paid for by lottery and council tax payers.

Straw told MPs that Livingstone might be painting a different picture but "what I say is the truth".

He said: "Let me say as chairman of the Cabinet Committee on the Olympics that I think the culture secretary was right and not wrong in publishing detailed figures so that there could be a judgment made."

He added: "Ken can write as many blank cheques as he wants, the thing is they won't be banked or paid because it is a matter for the Government to decide."