The High Court will hear a legal challenge to the practice of treating 17-year-olds detained in police custody as adults, in a judicial review being brought by Just For Kids Law next week.

The charity questions the legality of the Police and Criminal Evidence Act code of practice and the failure of the government and police to provide adequate support and protection to the 75,000 17-year-olds held in police custody each year.

The United Nations Convention on the Rights of the Child states that every person under 18 must be treated as a child, unless the age of majority in their country is reached earlier. In the UK the age of majority is 18.

But under the PACE code of practice, issued by the home secretary, 17-year-olds are treated as adults and only given the protections afforded to other children at the discretion of the police. Those discretionary protections include access to an appropriate adult.

Just for Kids Law and Doughty Street’s Caoilfhionn Gallagher will argue that this puts the home secretary and the Metropolitan Police in violation of both international and domestic law.

They will also challenge the failure of the Met to comply with its statutory duty to safeguard and promote the welfare of children, under section 11 of the Children Act 2004.

The High Court challenge highlights the case of a 17-year-old boy with no criminal record who was detained at a London police station for 12 hours overnight on suspicion of robbery, before being released without charge.

His family was not told of his whereabouts for hours, even though he had specifically asked for his mother to be informed and for her assistance at the police station, and he was not offered the help of an appropriate adult.

Director of Just for Kids Law Shauneen Lambe said the case is not an isolated one: ‘17-year-olds are routinely treated as adults when dealing with the police, with detrimental consequences for the children. Just for Kids Law believes that all children should be entitled to the same protection in the law.’

The Howard League for Penal Reform and the Coram Children’s Legal Centre were given permission to intervene and make written legal submissions to the court. The case will be heard on Tuesday.