Up to 5.9million children face having their fingerprints taken by schools in another move towards a 'Big Brother' society.
Pupils will have to hand over their biometric details simply to borrow library books or gain access to school dinners.
A million children's fingerprints are believed to have been taken already, some without parental approval and even by 'con tricks' such as pretend spy games.
Freedom of Information data obtained by the Tories reveals a further 4.9 million sets of prints could now be added to school computers after the vast majority of local education authorities sanctioned the practice.
Critics say it is part of a 'softening-up' exercise to condition children to accept a creeping surveillance society. They also point to the danger of identity theft, if hackers manage to access school databases.
Phil Booth, of the NO2ID campaign, said: "This is an abrogation of moral duty. Schools should be teaching children to look after their biometric information.
"They are going to grow up in a world where keeping it secure is enormously important, yet they are being taught that it is OK to hand it over for the most trivial of matters. It is a disgrace."
He added the Government could ultimately seek access to huge amounts of sensitive information by the 'back door'.
More than 3,500 schools already use systems which allow pupils to take out books by scanning their thumbprints instead of using a card. The technique is also being used in dinner queues.
Now the Conservatives have surveyed every education authority in the country to see if they allow the practice. Only 39 of the 171 that replied said they do not allow it. This means that up to 17,000 schools, with a total of 5.9million children, may already be allowed to fingerprint.
The Tories say that, in some cases, it is being done without parents' permission. Last month, it emerged a primary school headmaster had persuaded pupils to give their prints by pretending they were playing at being spies.
He reportedly told youngsters at Ghyllside Primary School in Kendal, Cumbria, it was 'just a game ... so there's no need to tell your parents'. The prints are used to operate the school's new library system.
Tory frontbencher Damian Green called for a new code to protect youngsters, consisting of the following four points: