Tony Blair has said he thinks "in principle" that identity cards are a good idea in a world with massive cross-border migration and high levels of benefits fraud.
During prime minister's questions, he said MPs would have to wait for next month's Queen's Speech to see if ID cards were on the legislative agenda.
Mr Blair was responding to a question from Liberal Democrat leader Charles Kennedy who asked the prime minister his opinion on the introduction of identity cards.
Home Secretary David Blunkett has already said that he wants to push forward with the scheme - despite reported discontent about the plan within the rest of the cabinet.
Iain Duncan Smith used his questions to attack Mr Blair over Council Tax rises and pensions.
Biggest stealth tax?
The Tory leader said Council Tax had become the government's biggest stealth tax of all.
Mr Duncan Smith quoted a minister saying that Council Tax bills had reached the limit of acceptability.
Mr Blair said: "We have said we will use the capping powers if necessary,
in respect of unacceptable Council Tax rises.
"But I would point out that we have funded a 25% real terms increase in the money going to local government since 1997.
"And in the end, of course, it is for councils to decide their levels of
The Tory leader then attacked what he called "persistent pensioner poverty", which he said had risen since 1997.
Mr Duncan Smith in particular singled out means testing which he said now involved six million pensioners - up two million from when Labour came to power.
He called on the prime minister to scrap means testing and increase the state pension.
Mr Blair said the government would make no apology for helping the poorest pensioners the most.
He said the previous Conservative government had abolished the link between pensions and earnings - a policy Mr Duncan Smith now wants to reverse.
And he argued the 1.4m pensioners receiving the means tested pensions credit were "absolutely delighted".
Mr Blair, Mr Duncan Smith and Mr Kennedy all paid tribute to Lord Williams of Mostyn - the Labour leader of the Lords - who died suddenly in September.