The home secretary should shelve his plans for national ID cards following a damning MPs' report, civil liberties groups have said.
MPs have grave concerns about the ID card scheme
A coalition of anti-ID card groups, called No2ID, has pledged to bring about the defeat of the plans when they are introduced to Parliament.
The Liberal Democrats say they would oppose any such bill, while the Tories say the plans are "fatally flawed".
The home affairs committee said the plans carried risks for the individual.
NO2ID's national co-ordinator Mark Littlewood said: "With opinion polls showing that around 3.5m adults would refuse to carry a card, the government needs to ask itself exactly how many more enemies it can afford to make.
Shami Chakrabarti, director of civil rights group Liberty, who is part of the NO2ID coalition, said: "It is no surprise that the committee's searching inquiry has produced such a critical report.
"Our experience is that the more closely people study Mr Blunkett's grand plan the less credible and attractive they find it."
Dr Ian Brown, director of Foundation for Information Policy, said the committee had raised some "very grave concerns" about the scheme.
"ID cards won't tackle terrorism, won't cut fraud and won't reduce crime.
"The government's plans are an expensive, dangerous folly," he added.
Liberal Democrat home affairs spokesman Mark Oaten said Mr Blunkett had failed to demonstrate that his plans would prevent terrorism or cut crime.
"The £3bn cost of ID cards would be better spent on getting more police on to our streets and ensuring that the intelligence services are properly resourced to tackle terrorism."
He added: "The Liberal Democrats will oppose the ID cards Bill in the autumn and I urge Conservative and Labour MPs to join us."
Shadow home secretary David Davis said the viability of biometric technology remained unproven.
"The committee are also clear that ID cards on their own are not the solution to terrorism and illegal working that David Blunkett claims they are.
"If the home secretary carries on like this, we will end up with a scheme that is both fatally flawed and so far in the future as to be irrelevant to the problems of today."