The Children's Society said unnecessary and invasive searches of young people must end and called for more police training.
A freedom of information request by RADAR shows Devon and Cornwall Police carried out 129 strip searches on under 18-year-olds in custody and under stop and search powers in the three years to March.
This included 29 searches last year.
Strip searching does not necessarily denote nudity or exposure of intimate body parts, though it can do, and it ranges from the removal of a shirt to the removal of all clothing.
They can be carried out in police custody or after a stop and search.
Across the 34 police forces that provided data in England and Wales, over 5,600 strip searches were carried out on children in the past three years. About 1,850 of these were in 2023-24.
None of the strip searches were carried out on children under the age of 10.
Mark Russell, chief executive of the Children's Society, said: "Strip searches of children are distressing, traumatic, and should be used only as a last resort and always with a trusted adult present.
"The police watchdog, the Independent Office for Police Conduct, has made it clear: children’s safety and wellbeing must come first. Police officers must be properly trained to handle these situations responsibly."
He added police dealing with young people should be able to spot signs of harm and connect them to the appropriate services to ensure their safety and support.
"Above all, children deserve to be treated with care and dignity. The days of unnecessary, invasive searches must end," he said.
Earlier this year, the IOPC made recommendations to improve how strip-searching of children is conducted. This included requiring police forces to make mandatory safeguarding referrals for any child subject to an "exposure of intimate parts" search.
Overall, the figures show a total of 6,265 strip searches were carried out across all age groups in Devon and Cornwall since 2021-22. It means children accounted for 2% of searches in the area.
Devon and Cornwall Police received 10 complaints about strip searches in recent years.
A Home Office spokesperson said strip search is one of the "most intrusive powers" available to the police.
They added: "Any use of strip search should be fair, proportionate and carried out with full regard for the dignity of the person being searched, especially children. Whilst there have been improvements, it is clear standards are not always being followed as they should.
"The Government has committed to introducing new safeguards for strip-searching children and young people in its manifesto."