The NHS computer system has been hit by delays and cost over-runs

The government is to scale back its £12bn NHS IT system in what the Tories are calling a "massive U-turn".

Chancellor Alistair Darling said he would be delaying parts of the scheme in Wednesday's pre-Budget Report as it was "not essential to the front line".

The move may save hundreds of millions but Mr Darling admitted it was only a fraction of total spending cuts needed.

The Tories and Lib Dems have been calling for the IT system, which has been hit by costly delays, to be axed.

Mr Darling told BBC One's Andrew Marr show he was determined to halve Britain's budget deficit over the next four years and as a result public spending would be "a lot tighter than it was in the past".

He stressed that the pre-Budget report was not a spending review, but added: "I do think it is necessary for me to indicate areas where we are going to cut spending or where we're not going to spend as much as we were.

"For example, the NHS had a quite expensive IT system that, frankly, isn't essential to the front line.

"It's something I think we don't need to go ahead with just now."

He said the full picture of cuts would not emerge until "the first half of next year at some point" - a reference to the comprehensive spending review, which the government has delayed until after an election.

'Procurement disaster'

Treasury officials have stressed that only part of the NHS IT programme is facing the axe, and the whole project will not be scrapped.