Nearly one million innocent people's DNA records could be wiped from the national database after the EU ruled that it breaches human rights.
The decision by the European Court of Human Rights means that the DNA details, and possibly fingerprints, of about 850,000 people suspected of a crime, but later cleared, could be removed.
The court found that, in keeping the DNA details of people suspected of a crime, the "state had overstepped any acceptable margin of appreciation".
The case was brought by two Britons, Michael Marper and 'S', who were cleared of crimes and challenged the government over their details being kept on the database, which holds details on 4.5 million people.
A Home Office spokesman said the government had until next March before it has to take any action as a result of the ruling.
Home secretary Jacqui Smith expressed dissatisfaction with the verdict, saying in a statement: "DNA and fingerprinting is vital to the fight against crime, providing the police with more than 3,500 matches a month, and I am disappointed by the European Court of Human Rights' decision."
"The existing law will remain in place while we carefully consider the judgement," Smith said.
Privacy pressure group NO2ID welcomed the decision, with the organisation's national co-ordinator, Phil Booth, describing it as a victory for liberty and privacy.