Figures have revealed Thames Valley Police took an average of 33 DNA samples from children every week in 2011.
The Howard League for Penal Reform charity say its research has found officers took swabs from 1,736 boys and girls aged 17 or under.
They included 41 primary school-age children along with 14 from 10-year-olds and 27 from 11-year-olds.
Many of the children required to give a sample will not have been charged with a criminal offence.
And across England and Wales, police took swabs from almost 54,000 boys and girls aged 17 or under during 2011.
Last December, the Howard League published data which showed the total number of children arrested by police had fallen by a third between 2008 and 2011.
Under current rules, police can retain indefinitely the DNA of anyone they arrest for a recordable offence.
A new law, imposing tighter restrictions on DNA retention, is expected to come into force later this year.
Charity chief executive Frances Crook, said treating so many children like 'hardened criminals' seems 'excessive'.
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