Fifty-thousand children in England and Wales have had their DNA added to a police database without being convicted, it has emerged.
The Home Office says inclusion does not signify a criminal record
Earlier this year, the Home Office revealed the database contained DNA profiles of 27,000 under-18s arrested but released without charge or caution.
It has now admitted DNA from a further 20,000 youngsters who have since turned 18 was taken in the same way.
The Home Office says there is a "clear public benefit" to keeping samples.
The further 27,000 DNA profiles were revealed in answer to parliamentary questioning from Conservative MP Grant Shapps.
A report, backed by campaigner Mr Shapps, says the DNA of 600 "innocent" children is being added to the database each week.
"This is, of course, coming at a time where the government has accidentally let out some pretty serious foreign criminals from our prisons without considering deporting them," Mr Shapps told BBC News.
"At the same time, they're allowing literally 600 children a week, entirely innocent, to be added to the DNA database without even stepping in saying anything about it at all and I think it's completely out of proportion."
In February, the Home Office announced DNA profiles would continue to be stored saying the samples helped to catch criminals.
At the time, ex-Home Office Minister Andy Burnham said there was a "clear public benefit" to keeping the samples and the existing policy was justified.
"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," he argued.