The Conservatives have raised fresh doubts over plans to introduce identity cards for British nationals after they appeared to have been delayed until 2012.

Documents leaked to the Tories showed that plans to "issue significant volumes" alongside passports for UK citizens would be put back two years from the original 2010 deadline.

Foreign nationals will still be issued with the cards this year as intended.

Shadow home secretary David Davis said that recent data security breaches had left the scheme "in the intensive care ward".

However, Number 10 said ID cards "can help deal with the issue of potential identity theft" and ministers insist the scheme will be "rolled out incrementally".

The prime minister's spokesman said that ministers had not made any decisions to change the original strategy set out in December 2006.

"That made clear that the first ID cards for British citizens would be issued in 2009 and that the role out would be on an incremental basis," said the prime minister's spokesman.

Asked whether the scheme would be introduced on a voluntary basis for UK citizens in 2009, he said: "It would be voluntary unless a vote in Parliament made it a compulsory scheme and whether we ask Parliament is a matter for the future."

Timetable

The document set out a timetable for introducing the biometric cards, which are expected to cost about £5.6bn.

It said that "Borders Phase I" for foreign nationals would start later this year, but that "Borders Phase II" for Britons would be delayed until 2012.

Davis said: "The government's ID card project has lurched from shambles to shambles. Now it is in the intensive care ward.

"It is a project that will do nothing to improve our security and may actually threaten our security."

The Liberal Democrats also oppose the plans, with party leader Nick Clegg saying he would rather face jail than provide his data to obtain a card.

Roll-out

The Identity and Passport Service refused to comment on the leaked report, but a spokesman said: "We have always said that the scheme will be rolled out incrementally.

"The framework procurement for the scheme is currently underway: we will make further announcements about the rollout of ID cards in due course."

He added: "As stated in the strategic plan for the national identity scheme published in December 2006, we will begin issuing ID cards for foreign nationals this year, and the first ID cards for British citizens in 2009.

"By linking fingerprints to a secure database with strict rules outlining its use, the national identity scheme will allow individuals, business, and the state to prove identity more securely, conveniently and efficiently while protecting personal information from abuse.

"The Identity and Passport Service successfully introduced the first biometric passport on time and on budget in 2006, with over eight million now issued.

"The next move is to include fingerprints in a second generation biometric passport, in line with international developments in passport security."