Mactaggart declared in an article in The Guardian last week that she was now supporting the Government's proposed introduction of identity cards, championed by Home Secretary David Blunkett, her departmental boss.
She wrote that her change of mind was prompted by biometrics: "An iris print, fingerprint or face scan will revolutionise the way in which we identify ourselves over the next 10 years."
Liberty has responded by drawing attention to Mactaggart's opposition to identity cards last year, before she became a minister. " A card which is being proposed as a passport to social inclusion will provide the first national mechanism to organise social exclusion," she wrote in a Liberty pamphlet.
Shami Chakrabarti, director of Liberty, said: "Invoking biometrics is a nonsensical argument because nothing has changed on that front in the 15 months since she declared herself against identity cards."
Mactaggart also said in her Guardian article that "there will be no new powers for the police to demand identity cards, and we will be working with the Commission for Racial Equality and others to make sure that it does not have an unfair impact on ethnic minorities."
Chakrabarti responded that it will take 10 years to get the system working, "and we have no idea to what use the government of the day will put identity cards".