Identity cards are opposed by the Tories and Lib Dems
Gordon Brown has not changed his mind on identity cards despite speculation he is preparing for a U-turn, a home office minister has told the BBC.
Meg Hillier said the PM had "made it very clear" he supported the scheme.
Tory leader David Cameron has written to Mr Brown asking for clarification after a Commons clash over whether he wants them to be compulsory or not.
Lib Dem leader Nick Clegg said he believed there had been a "significant shift" in the government's position.
The row was ignited by an interview Mr Brown gave to a Sunday newspaper in which he said: "Under our proposals there is no compulsion for existing British citizens".
Challenged about his comments by Mr Cameron in the Commons, Mr Brown said: "It is the government's policy to move ahead with this but subject, I have to tell him, to a vote in Parliament depending on how the voluntary scheme works."
Mr Cameron later wrote to the prime minister requesting a clarification.
He wrote: "Anyone watching will have been left in considerable doubt about whether you personally support compulsory ID cards and will recommend this approach to the House of Commons".
He added: "Could you now answer this very simple question: Do you personally support a compulsory ID Card system for British nationals?"
Nick Clegg, who has said he would be prepared to go to jail rather than carry an ID card, said the government had clearly shifted its position on the controversial scheme.
"I detect a death by a thousand cuts," Mr Clegg told BBC Radio 4's PM programme.
He contrasted Mr Brown's stance with the approach of his predecessor Tony Blair, who in 2006 offered MPs a future vote on compulsion as part of a deal to get the legislation through the Commons.
"Let's be clear, the government was forced, through gritted teeth, to concede there would be a separate vote on compulsion, but always made clear at the time of that debate and that vote that compulsion was necessary for the scheme to work.
"For the prime minister now to tiptoe away from that I think is an extraordinary admission of defeat," Mr Clegg added.
But junior Home Office minister Meg Hillier said there was no question of a U-turn on ID cards.
"ID cards are going ahead. We had the act of Parliament passed.
"I am busy working at proposals now for how exactly we will be doing that and in due course the home secretary will be making announcements about how that will happen."
She said speculation about a change of heart had "got a bit heated unnecessarily".
"We always said there would be a further vote in Parliament about identity cards," added Ms Hillier.
"And we always said that any discussion about compulsion would only come after a scheme was implemented on a voluntary basis and had acceptance.''
She said Mr Brown had "made it very clear he is supportive" of the scheme.
Earlier, Keith Vaz, Labour chairman of the home affairs select committee, said he also believed the government had shifted its position, in the light of recent data loss scandals.
Asked if the prime minister was creating "wriggle room" - for fear he would not get the scheme through Parliament - Mr Vaz said: ''I think there may well be a little bit of nuances being created here.
He said his committee was to look again "at the issue of data protection in respect of ID cards because of what's happened over the last few weeks and the minister has agreed to come and see us in a fortnight's time and I think if there is going to be a change of policy, that will be a good opportunity to make it clear, that it has changed".
Mr Vaz said ID cards for foreign nationals, which are being introduced later this year, were effectively being used as a pilot to "see whether or not the information is then subsequently lost".
"I don't think they can take another major loss of data in this way and that's why the select committee is going to look at it again," he added.
Former Home Secretary David Blunkett, who introduced the initial identity card bill, told the BBC on Tuesday the scheme would not work unless everyone had to have a card.
"In my opinion, without it being mandatory, there is little point in doing it," he added.