The government has been defeated twice in the Lords over its Identity Cards Bill, as opposition peers attempt to make the scheme entirely voluntary.
Peers also voted against ID cards last week
Ministers want applicants for passports and driving licences to be obliged to go on the ID card register.
But peers decided by 186 votes to 142 - a majority of 44 - to ensure that entry on the list is voluntary.
The government lost again when peers called for a separate Act of Parliament before cards could be made compulsory.
The votes were among a series of Lib Dem and Tory amendments aimed at making sure people have a choice.
Conservative leader David Cameron has called ID cards a "monument to the failure of big government".
His comments followed a report which estimated they would cost £14.5bn.
Tony Blair said the entire government "absolutely" backed ID cards and that fears over civil liberties were "misplaced".
Ministers say cards are needed to fight identity fraud and illegal immigration.
For the Tories, Baroness Anelay of St John's said the amendment would require the government to keep to its manifesto commitment to introduce ID cards "initially on a voluntary basis".
Liberal Democrat home affairs spokesman Lord Phillips said: "I hope this defeat will cause the government to think again about its flawed and expensive scheme."
Home Office minister Baroness Scotland of Asthal insisted the government had been "utterly straightforward and frank" about its intentions.
Last week, peers voted to block the scheme until its full costs were known.
The Home Office estimates the scheme will cost about £584m to run each year, with each combined biometric passport and identity card costing £93.
However, it has not given full estimates for setting up the scheme and says the overall expense will depend on how government departments choose to use the card scheme.
The government is likely to try to overturn the Lords defeats when the ID cards bill returns to the Commons.