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Jack Straw was accused last night of misleading MPs after it emerged that the cost of a huge prison building programme is almost double the £1.2 billion figure he gave Parliament.

The costs of providing an extra 10,500 jail spaces, including three “super-prisons” each holding 2,500 inmates, have been estimated at £2.3 billion.

Mr Straw, the Justice Secretary, disclosed the cost of the huge expansion of the prison estate during tough questioning at the Commons Justice Select Committee.

When he had announced the latest prison building programme last month, he said he had agreed with the Prime Minister for additional funding of £1.2 billion to bring the 10,500 spaces on stream by 2014.

At the select committee he said: “The gross cost is likely to be about £2.3 billion . . .”

Andrew Tyrie, the Conservative MP who forced Mr Straw to disclose the overall costs, said: “It was highly misleading of Jack Straw in his statement, which was a carefully considered prepared statement, to imply that the cost of implementing [the] proposals to 2014 would be covered by £1.2 billion.”

The row over the funding to meet key recommendations of a review of prisons by Lord Carter of Coles came after MPs on the Justice Select Committee had been informed that officials in the Justice Ministry were privately saying the actual bill was likely to be more than £2 billion.

Lord Carter, a friend of Mr Straw, recommended in December that an extra 10,500 jail spaces should be provided by 2014 to deal with a prison population that could be more than 100,000 within seven years.

His recommendations were on top of a £1.5 billion programme to provide 9,500 prison places by 2011.

Mr Straw accepted Lord Carter’s recommendations, which include proposals for three “super” Titan jails each capable of holding 2,500 inmates.

Cash is also to be spent on providing other accommodation, including converting RAF Coltishall in Norfolk into a Category C closed prison, looking for two prison ships, bringing forward existing prison modernisation schemes and paying for the monitoring of more offenders in the community.

Lord Carter recommended that one superjail be erected by 2012 with a further two by 2014, although Mr Straw announced only that “up to three large Titan prisons” would be built – casting doubt on whether three would be built given the mounting cost of the jail building programme.

Labour MPs inflicted their first significant revolt on Gordon Brown yesterday, with 35 opposing a ban on strikes by prison officers. Keith Vaz, the former Europe Minister, and Kate Hoey, the former Sports Minister, were among the Labour rebels as the measure was backed by a massive majority. The Government said that it was “reluctantly compelled” to seek the powers after a walkout by 20,000 prison officers.

Jack Straw introduced the amendment to the Criminal Justice Bill to allow the Government to reintroduce powers to ban strikes by prison officers.

He said it was necessary for public safety, and prisoners’ welfare, that prison officers did not strike. He has been accused of a “humiliating U-turn” by the Tories, who say in opposition Labour opposed a ban introduced in 1994.

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