The Tories have announced their intention to scrap identity cards if they win the next general election in an attempt to derail the government's plans to introduce them later this year.

David Davis, Shadow Home Secretary, hoping to frighten off any firms which may want to be involved in the project, wrote to Sir Gus O'Donnell, Cabinet Secretary, yesterday informing him of the party's intentions.

Mr Davis told the Cabinet Secretary he was giving him formal notice of the opposition's intentions.

"You will be aware that there is a long-standing convention that one parliament may not bind a subsequent parliament. As you will also be aware, the Conservative Party has stated publicly that it is our intention to cancel the ID cards project immediately on our being elected to government. You are now formally on notice of our position and fully appraised of the contingent risks and associated liabilities arising from the national identity card scheme," he said.

Mr Davis's letter was sent to coincide with today's start of the Tory party campaign against the introduction of national identity cards.

Around £58m has been spent so far on the scheme, which according to ministers will cost £5.4bn over 10 years. Mr Davis is warning that any money spent on ID cards could be money down the drain.