Tony Blair has defended his ID cards plans, saying he is confident that the public backs them in principle.
Mr Blair says some of the costings for ID cards are 'absolutely absurd'
The London School of Economics says the scheme could cost £19bn - more than three times government estimates.
Information Commissioner Richard Thomas said the plans "risk an unnecessary and disproportionate intrusion into individuals' privacy".
But Mr Blair said ID cards would cost less than £30 extra on top of the cost of the new biometric passports.
He argued, the day before the ID Cards Bill has its second reading in the Commons, that they were "an idea whose time had come".
"Some of the figures bandied around about cost are absolutely absurd," he said at his monthly news conference after the LSE report's publication.
"There are good reasons for doing this now, because of the change to technology, the fact that we will have to pay for biometric passports and the ID card part of it is a very small additional cost."
Biometric passports were needed to enable UK citizens to continue to enjoy the right to travel freely around the world, he added.
TEN KEY UNCERTAINTIES:
How much will the scheme cost the UK?
How often will cards/biometrics need to be renewed?
How often will cards be lost/damaged/need to be replaced?
How difficult to enrol people on to the scheme?
How easy will it be to verify people's identities?
Will public accept the plans?
What are the civil liberty/privacy implications?
Will disabled people suffer hardship and discrimination through the scheme?
Are there security concerns?
Could new ID fraud arise from cards coming into pervasive use?
Source: LSE report
The LSE says its "best case scenario" for the cost of the ID card scheme is £10.6bn (about £170 per card and passport). The worst case estimate is £19.2bn.
The government's estimate is £93 per card.
The LSE has identified "ten key uncertainties" over the project, including security concerns, how often would the cards need renewing and how difficult will it be to get people to use the scheme.
Professor Patrick Dunleavy, one of the LSE report's authors, said the school's academics had asked ministers to participate in their research but they had declined to do so.
He said the report was the result of extensive research into ID card schemes around the world and talks with industry representatives and academics.
The Conservatives, Liberal Democrats and some Labour MPs are expected to oppose the plans in the Commons.
David Davis, shadow home secretary, said: "This report raises many concerns relating to the cost, security and practicalities of the ID card proposals. The government has not addressed a single one of them."
Lib Dem home affairs spokesman Mark Oaten said the report "should be the final nail in the coffin for Labour's identity card proposals".
An almost identical bill was abandoned before the general election. A total of 19 Labour MPs rebelled over that bill.
The Lords is also expected to be a major stumbling block for the bill.
Shami Chakrabarti, director of human rights group Liberty, predicted ID cards would prove to be Tony Blair's poll tax.