Organised crime will try and crack the identity cards database — the National Identity Register (NIR) — the Liberal Democrats have warned.
Last year it was revealed that the identities of 13,000 civil servants had been stolen and used by criminals to make fake tax credit claims.
Liberal Democrat home affairs spokesman, Nick Clegg, said the theft was a "terrible omen" for the forthcoming ID cards scheme.
Clegg said, if organised criminals are capable of infiltrating the Department for Work and Pensions (DWP), "it is clear they will target the identity cards database, where the stakes are even higher."
Clegg said in a statement: "The government's claims that ID cards will cut identity fraud look increasingly unrealistic. If the ID cards database is breached, people could find their iris scans and fingerprints — as well as personal data and national insurance numbers — stolen."
He said the government must urgently review how the DWP thefts happened and whether it will be possible to secure the NIR against similar attacks.
Yesterday it was reported in The Times that more than 300,000 foreigners are given national insurance numbers every year with few checks on their status.