Concerns of fraud, computer overload and the cost of identity cards have been raised with a committee of MPs.
MPs and peers are still worried about possible cost overruns
Security safeguards for the cards were "no more" than that for chip and pin bank cards, a London School of Economics academic told the committee.
Computer Weekly's Tony Collins also voiced doubts over the ability of the government's IT systems to cope.
A Home Office spokesman said the government believed "proving who we are" was "fundamental".
'Grappling with capacity'
Mr Collins recommended conducting an audit of the scheme before any introduction.
Patrick Dunleavy, from the London School of Economics (LSE) said there could be a "possibility to fake up the card" and suggested there would be an "arms race" between criminals and the creators of the cards on how they could be used.
"It seems that biometrics will be used only to validate the cards at the beginning... it is like a chip and pin card but with an initial validity check," he said.
Professor Dunleavy said a team from LSE was "looking at the cost estimates".
Last week one of the authors of the LSE report said some parts of its estimates on the identity card cost should be reduced, but he suggested new costs could push the overall price even higher.
Ministers argue that accountants KPMG have concluded the government's estimates were "robust".
But, Mr Collins told the committee, the accountants' description referred only to the "methodology" of the estimates.
He recommended an ongoing "audit" of the scheme, warning that there did not appear to be any means of stopping the project mid-stream if it did not seem justified.
A Home Office spokeswoman denied the proposals lacked scrutiny. She said there had been both pre-legislative and ongoing scrutiny as the ID Cards Bill proceeded through parliament.
Referring to KPMG, she said: "They found the methodology of our estimates was robust and reliable and in order to reach that conclusion they had full access to our cost models."
Mr Collins, who is executive editor of Computer Weekly, questioned how well departments' IT systems could handle the introduction of the identity cards.
"I have covered government projects for over 15 years and seen a lot of projects go wrong," said Mr Collins.
He said some departments' computer systems dated back 20 years, were "highly complex" and were already "grappling with capacity issues".
It would be difficult to alter those systems so they could use the ID card numbering system, he suggested.
Mr Collins pointed to the breakdown of the Child Support Agency scheme where, he said, the cause of the problem "could not be established".
Asked specifically if the card scheme was "do-able", he replied: "If I could exercise extreme caution, I could be optimistic about the outcome."
He also argued the need for "transparency", saying the Home Office should make public the finer details of the scheme to allow for better public debate.