David Cameron is set to accuse Labour of wasting billions of pounds with its "secretive and inefficient" regime for handing out Government contracts.

The Tory leader is to promise 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 influential Technology, Entertainment, Design (TED) conference in California, he will highlight the "worst" deals struck by Whitehall since 1997.

The NHS IT system is £6 billion over budget and four years late, while modernisation of the National Offender Management System was £450 million 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 will say.