Several hundred children were subjected to strip searches in London over the last two years, newly released figures reveal.
Data shows that 650 children aged 10 to 17 underwent the practice between 2018 and 2020.
Dame Rachel de Souza, the Children's Commissioner for England, said she was "deeply shocked" that so many youngsters had been searched this way.
"In a strip search, your most intimate parts are searched," said de Souza. "For any child, that's going to be traumatic and concerning."
The data also reveals ethnic disparities, added De Souza.
She said 58% of children strip-searched over the two-year period were black, despite just 19% of 10-17 year-olds in the UK capital having this ethnicity.
The commissioner also found that in nearly a quarter of cases the search took place without the presence of a third adult.
More than half of the searches did not lead to a prosecution, with Dame de Souza saying they were probably not "warranted or necessary in all cases".
The commissioner launched her investigation following widespread outrage over the case of Child Q, a 15-year-old black schoolgirl who was strip-searched at her school in east London.
She was wrongly suspected of carrying cannabis.
The strip search prompted days of protests in Hackney after it emerged the schoolgirl was searched without another adult present and with the knowledge that she was menstruating. Her parents were not contacted.
In the UK, it is a legal requirement for an appropriate adult to be present during the strip search of a child, except in urgent situations.
A Child Protective Services report into the incident concluded that the search should “never” have taken place and that “racism (whether deliberate or not) was likely a contributing factor."
Strip searches on females are rare in the UK, with 19 out of 20 performed on males.
De Souza said her findings showed the case of Child Q was not a one-off.
“I am not reassured that what happened to Child Q was an isolated issue, but instead believe it may be a particularly concerning example of a more systemic problem around child protection within the Metropolitan Police," she said.
"I remain unconvinced that the Metropolitan Police is consistently considering children’s welfare and wellbeing."
She also expressed concern about "holes in the data" recorded by London's police force.
"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," de Souza said.
In a statement, the Metropolitan Police said it is "progressing at pace" to ensure children subject to intrusive searches are dealt with respectfully.
It added new measures have been introduced requiring an inspector to give authority before a search takes place.