The Children's Commissioner for England, Dame Rachel De Souza, has found thousands of cases of children being strip-searched across England and Wales.
Her research found Hampshire Constabulary carried out 133 strip-searches of children aged between eight and 17 from 2018 to mid-2022.
Dame Rachel described the practice as "intrusive and potentially traumatic" to children involved, adding it should be subject to greater safeguards and scrutiny.
The investigation comes after a fifteen-year-old black girl from East London known as 'Child Q' was strip-searched by the Met Police in 2020 without another adult present.
The incident sparked protests when it came to light in 2022.
The research revealed a total of 2,847 strip-searches took place between 2018 and mid-2022 of children aged between eight and 17 across England and Wales.
The report noted as several forces did not respond to their request, this figure should be considered a minimum.
The Met Police was responsible for nearly a third (31%) of all searches.
Dame Rachel said: "We’ve seen growing evidence that children are being failed by those whose job it is to protect them."
"Much more work is required to create a culture among the police in which children are, first and foremost, treated as children," she added.
Dame Rachel further praised the bravery of Child Q for coming forward.
Across England and Wales the vast majority of youngsters strip-searched were boys (95%) and about 38% of children strip-searched were black.
Police guidelines state searches should only be carried out within view of officers of the same gender – but the Commissioner found 6% had taken place in the presence of an officer of another gender.
The report found black youngsters were up to six times more likely to be strip-searched compared with national population figures, while white children were around half as likely to be searched.
Chief Constable Craig Guildford, lead for the ethics and integrity portfolio at the NPCC – a staff body for police chiefs – said they will “carefully consider the findings” of Dame Rachel’s report.
He said it is “vital that any police interaction is handled sensitively, and that, when an officer considers it necessary to search a child, that it is carried out in line with legislation, policy, and procedure”.
He added: “We are working closely with the College of Policing, IOPC and other partners in order to inform best practice and to implement positive change wherever it is required.”
A Home Office spokesman said: “We take the concerns raised about children’s safeguarding extremely seriously. The Independent Office for Police Conduct is currently investigating several high-profile incidents of strip-search of children and it is vital that we await their findings.”