Allowing children to be used as informants in criminal investigations is lawful, the High Court has ruled.
Charity Just for Kids Law brought the case against the Home Office over the use of children by police and other bodies in England and Wales.
The campaign group said the safeguards in place were inadequate and the practice breached human rights.
But the High Court rejected the legal challenge, saying there was a “system of oversight” in place.
In March it was revealed that 17 children had been used to secretly gather intelligence for police and other agencies in the last four years.
Lord Justice Fulford, the Investigatory Powers Commissioner who is carrying out a review into the use of children as covert human intelligence sources (CHIS), said one of the informants was 15 years old, while the others were aged 16 and 17.
The Home Office had argued that undercover under-18s helped prevent and prosecute problems such as gang violence and dealing drugs.
However, concerns over the use of juveniles were raised in the House of Lords last year with the case of a 17-year-old girl who was recruited to spy on a man who had been exploiting her sexually.
The peers heard that the girl continued to be exploited sexually while she was deployed by police.
Charity may appeal
Dismissing the charity’s case, Mr Justice Supperstone said he was satisfied the scheme was lawful.
The judge said children were “inherently more vulnerable than adults” and that the “very significant risk of physical and psychological harm” to them from being a CHIS in the context of serious crime is “self-evident”.
However, he said he rejected the charity’s contention “that the scheme is inadequate in its safeguarding” of the juveniles involved in the scheme.
Just for Kids Law, which used crowdfunding to pay for the case, said it was disappointed and was considering whether to appeal against the decision.
The charity’s chief executive, Enver Solomon, said the judgement acknowledges the ‘”variety of dangers” that arise from the use of children as covert informants in the context of serious crime.
He added: “We remain convinced that new protections are needed to keep these children safe.”
Security minister Ben Wallace said the ruling showed the court recognised that the protections in law ensure “the best interests, safety and welfare of the child will always be paramount”.
Children had been used as informants fewer than 20 times since January 2015, he said, but they remained “an important tool to investigate the most serious of crimes”.
He added: “They will only be used where necessary and proportionate in extreme cases where all other ways to gain information have been exhausted.”