DNA samples from 339 innocent Cheshire teenagers are being stored by police.
The revelation triggered Conservative claims the Government was building a 'DNA database by stealth' - with both the guilty and innocent side-by-side.
But the Government rejected demands that the samples - gathered from under-18s arrested, but never convicted or cautioned - should be deleted.
Instead Home Office minister Andy Burnham insisted the practice, introduced in 2001, enabled police to match 541 teenage samples to crime scenes from unsolved offences nationwide.
Mr Burnham added: 'Inclusion on the database does not signify a criminal record and there is no personal cost or material disadvantage to the individual simply by being on it.
'Given this, and the clear evidence showing the substantial benefit in relation to the detection of serious crime, it is the judgment of the Government that the existing policy is justified.'
The figure for Cheshire is higher than in some neighbouring forces; Merseyside is storing 80 samples.
Conservative home affairs spokesman Damian Green said: 'It is clear the Government is determined to set up a national DNA database by stealth.
'It is completely unacceptable for this intrusion into our lives to be made without Parliament having the chance to debate this dubious policy.'
Until May 2001, police were required to destroy DNA samples and fingerprints of anyone arrested - but not charged - with a recordable offence.
When the law was changed ministers insisted the decision on retaining samples was an operational one for chief constables.
A spokesman for Cheshire Constabulary said: 'The legislation on the retention of DNA profiles is clear.
'However, these powers are permissive so it is an operational decision for the police whether to take a sample.'