Almost 600,000 genetic profiles taken from innocent people have helped swell the National DNA Database to cover about seven per cent of the UK population.

Home Office figures also reveal that DNA profiles from 39,095 children who have never been charged, cautioned or formally reprimanded are now on the database indefinitely. Two years ago there were 24,000 profiles from ten to 17-year-olds stored. In 2004 police were granted powers to take DNA from everyone they arrest irrespective of the outcome of the investigation. According to the data released by junior Home Office minister Meg Hillier, almost half of profiles retained in the last two years are from such cases.

Opposition parties criticised the policy. Liberal Democrat home affairs spokesman Chris Huhne said: "There can be no excuse for storing the DNA of innocent adults, let alone children, who are entirely blameless." The Tories called on the government to allow a parliamentary debate on the issue.

That could prove unnecessary, however. A legal challenge by two Sheffield men is currently under consideration by the Grand Chamber of the European Court of Human Rights in Strasbourg. If it finds in their favour the government could be forced to remove all the DNA profiles it retains from innocent people.