Tory MP Grant Shapps obtained the Home Office figures when a constituent's son was wrongly arrested and DNA taken. After protests, the local chief constable agreed to remove the boy's details, but Mr Shapps then discovered that profiles of 24,000 youngsters aged 10 to 18 were stored.
"Police can take information without asking permission from parents since a change in the law in April 2004 and you can't get details removed even though they are not guilty," he said.
Shami Chakrabarti, director of Liberty, the human rights group, said: "This is the Prime Minister's vision of criminal justice - guilt determined by police officers, rather than the courts."
Concerns were raised earlier this month, when it was disclosed that 7 per cent of the population are expected to be on the database by April 2008. Five per cent (just over three million) are thought to be on it already.
Home Office minister Andy Burnham told Radio 4's Today programme that the database was "not a criminal record". He insisted: "There are proper safeguards in place as to how information can be used."Reuse content