The children's commissioner has said "sorry isn't good enough" after it emerged children are being strip-searched by the Metropolitan Police without an appropriate adult present in almost a quarter of cases - with black boys disproportionately targeted.
The research, published by the commissioner, revealed that officers in the force conducted intrusive searches on 650 young people aged 10 to 17 between 2018 and 2020.
It was commissioned after the case of Child Q, a 15-year-old black girl who was strip-searched at her school in east London without an appropriate adult present. She was wrongly suspected of carrying cannabis.
Dame Rachel de Souza, the children's commissioner, said the case had been wrongly described as "a one-off".
She told Sky News: "I am really shocked and sad to say it is not."
Dame Rachel called on all police forces across England to report data on how many children have been strip-searched.
"I want to see change," she said. "Sorry is not good enough."
She added: "In 50% of those strip searches, no further action was taken. That really raises questions for me about whether they were proportionate and should have been undertaken."
The experience, she said, would be "traumatic" for any child: "In a strip search, your most intimate parts are searched."
Dame Rachel also said she was concerned about "holes in the data" recorded by the Met Police.
"For about one in five of the strip-searched, they can't even tell me where they took place, so the data collection needs to be better."
It is a legal requirement for an appropriate adult to be present, except in urgent situations.
Of the 650 children who were searched in the three years, 19 in every 20 were boys and 58% were described by the officer as being black.
Katrina Ffrench, the founder and director of Unjust UK, a non-profit organisation that seeks to address discrimination in the criminal justice system, said she was "incredibly horrified" by the figures.
"The numbers are so high because they demonstrate that there's an issue within the Metropolitan Police and its treatment of black communities across London," she said.
"Unfortunately, young black children are not afforded innocence and the same rights as their white peers."
In 2018, more than two thirds of those strip-searched without anyone else present were black boys.
Kevin Donoghue, a solicitor who has represented children elsewhere in the country who have been through the experience, said: "The fallout for these children is very significant. The common features and expressions given to me in handling these cases are one of personal intrusion.
"There is a violation by police officers which is very severely felt and one of personal integrity and their bodily autonomy which has been invaded and it is an event which cannot be undone.
"An apology is not enough. Compensation is not enough."
In the case of Child Q, four officers are under investigation for gross misconduct and a serious case review has been carried out.
The Met Police said that it is "progressing at pace" to ensure children subject to intrusive searches are dealt with respectfully.
It said new measures have been introduced requiring an inspector to give authority before a search takes place.
The force added: "We have ensured our officers and staff have a refreshed understanding of the policy for conducting a 'further search', particularly around the requirement for an appropriate adult to be present.
"We have also given officers advice around dealing with schools, ensuring that children are treated as children and considering safeguarding for those under 18."