A school could be breaking the law by confiscating pupils’ phones and refusing to hand them back for weeks on end, a lawyer has claimed.

City of London Academy Islington is embroiled in a legal row over its new hardline policy of hanging on to mobiles – refusing even to return them to parents – until the end of term.

One lawyer has said the school is on “questionable” ground and could be violating pupils’ human rights or even be guilty of theft.

Greg Foxsmith, a human rights solicitor and Lib Dem councillor for Hillrise ward, said: “It’s a very draconian punishment.

“The school is entitled to take mobiles until the end of the day, but to retain the phone until the end of term is arguably a human rights breach and it could even be a theft because they’re depriving that person of their property.

“I think the school is on questionable ground.”

Pupils are banned from bringing in mobiles under the policy, brought in by new headteacher Mark Emmerson, who took over last month.

Cllr Foxsmith has offered to take up the case of one 12-year-old pupil after her �300 BlackBerry was seized last Tuesday.

Noorie Khondakhar’s phone was taken after she was seen checking messages on her way out of the school, in Prebend Street, Islington.

Her mother, Aysha Akter, 32, of Burder Close, Newington Green, said: “I went in the next day to get the phone but the headteacher just point blank refused. I did some research and I think there are legal issues.

“The school has not factored in parents’ needs. I gave my daughter the phone because she has responsibilities. She has to pick up her little sister from primary school sometimes, and there’s a safety concern. I need to make sure my children are OK after school.”

Property is protected under human rights law, but schools have powers to confiscate and retain items when it is reasonable or proportionate to do so.

Noorie’s step-dad Daniel Money, 31, said: “This is not a reasonable punishment – it’s over the top and it’s a complete power trip.”

Ken Muller, of the National Union of Teachers’ Islington branch, said: “The use of mobiles during lessons is very disruptive and clearly can’t be permitted, but refusing to return phones to parents does not seem to me to be reasonable and is possibly an infringement of the law.”

Richard Regan, chairman of the academy’s board of governors, said: “Pupils will achieve good academic results by learning in a high-quality teaching environment and adhering to an appropriate behavioural code.

“Mark Emmerson was appointed executive head in April and has immediately addressed both of these issues, which includes introducing a ban on the use of mobile phones in school.”

The school, which had some of the worst GCSE results in the country last year, has not revealed how many phones have been confiscated.