David Cameron has accused Labour of wasting billions of pounds with its “secretive and inefficient” regime for handing out government contracts.

The Tory leader has promised to restore public trust in the system by publishing in full all contracts for goods and services worth more than £25,000.

In a video-link speech to the Technology, Entertainment, Design conference in California, he highlighted the “worst” deals struck by Whitehall since 1997.

The NHS IT system is £6bn over budget and four years late, while modernisation of the National Offender Management System was £450m over budget before being partially shelved in 2007, according to Mr Cameron.

Publishing contracts in full from January 2011 - including all performance indicators, break clauses and penalty measures - will allow people to root out wasteful spending, and help small businesses win more government contracts, he said.

Speaking ahead of Mr Cameron’s speech, shadow chancellor George Osborne said: “The Conservative Party will call time on Labour’s era of wasteful spending, which has seen billions of pounds wasted on poorly negotiated and ineffective contracts.

“Our commitment to publish government contracts in full is the most radical transparency announcement ever made by a British political party - and will enable the public to hold ministers and civil servants to account like never before.

“This policy will help us to cut government spending, root out waste and empower the public - and bring in a new age of transparency and accountability.”