Cases may end up going through the courts with minor offenders likely to escape with a police reprimand – but even that would show up on some Criminal Records Bureau (CRB) checks, potentially damaging the career prospects of those involved.

Police regard the tactics as successful and are now planning education sessions in schools about the consequences of using other people's passports and other documents, but legal rights organisations are worried.

Police have known for some time that under-age drinkers use borrowed, stolen or forged identity documents to sidestep the Challenge 21 system, which demands proof of age.

Now officers in Sheffield have started arresting those found trying to misuse documents under new legislation which has made it an offence to misrepresent documents for identification purposes.

Police say they have support from the licensed trade, which believes under-age drinkers are bad for business. Door staff have been frustrated by customers using documents to "prove" they are old enough to be allowed in.

Because adolescents can change appearance quite dramatically, even passport photographs are difficult to dispute.

Signs warning of the consequences of breaking the law have now gone up at premises in the Challenge 21 scheme and the first case has been sent to court.

The reprimands issued would show up on extended CRB checks, meaning anyone involved could face future employment problems. The legal reform organisation Justice has warned that "minor offending" should not be allowed to compromise long-term employment opportunities.

South Yorkshire Police Insp Neil Mutch said: "It has got to the point where we have been getting lots of abuse of documents, with people using different people's passports, for example, with old photographs where there is a lot of debate about whether or not it is the same person.

"We have recovered loads of passports which have been misused. It is a nightmare.

"We have started arresting people and processing them. We have done it for around six weeks so far and 30 people have been arrested. It is one way of trying to keep kids out of clubs."

He added: "The Act was brought out for terrorism, but it suits us very nicely."

The age of those involved means that most will be dealt with through a police reprimand, although one is going through the courts.

"These are people who ordinarily would not get into trouble with the police," Insp Mutch admitted.

Police are now planning schools education work from the start of the autumn term.

Caroline Willow, of the Children's Rights Alliance, said: "We have strong concerns and would question what alternative methods of dealing with this problem have been considered and ask why they feel there is no alternative to using terrorism legislation, which wasn't drafted with this intent."

A spokeswoman for Justice said: "While we agree that young people must be deterred from breaking the law, this is not to say that their long-term education and employment prospects should be harmed by minor juvenile offending.

"We hope that universities, colleges and employers would take a sensible attitude, but there is also a strong case for minor juvenile offences to be subject to removal from ordinary CRB checks after an appropriately short period. Otherwise young people may continue to offend, perhaps more seriously, because other avenues are closed to them."