The New South Wales police performed strip-searches on more than 100 girls in the last three years, including two 12-year-olds.

Following the NSW police watchdog’s investigation into the allegedly illegal strip-search of a 16-year-old girl at a music festival last year, data obtained under freedom of information laws show she was just one of 122 girls under the age of 18 who have been forced to undergo the controversial practice by police since 2016.

The revelations come as the NSW police watchdog revealed last week that it investigated six separate allegations of misuse of strip-search powers by police last year, and is likely to place the practice under increased scrutiny.

The data, obtained by the Redfern Legal Centre, reveals that since 2016 there have been 3,919 strip-searches by police on women in NSW. Young women aged 25 and under accounted for almost half the searches, while the oldest woman strip-searched was 72 years old.

Most shockingly, the data shows that two 12-year-olds and eight 13-year-olds have been strip-searched by police since 2016.

“Girls as young as 12 and 13, some just finishing primary school, are being taken by police to a strange place and ordered by someone with a huge amount of power to take off their clothes,” Samantha Lee, the head of police accountability at the Redfern Legal Centre said.

“There is no doubt these young women would have been scared, some terrified and most having no idea of their legal rights.”

Last month the Law Enforcement Conduct Commission held public hearings as part of its investigation into the allegedly illegal search of a 16-year-old girl at the 2018 Splendour in the Grass festival. She was one of seven children who were strip-searched at the event.

The inquiry heard the girl was left fearful and in tears after she was forced to strip naked and squat in front of a police officer who then “looked underneath” her. The search took place without a parent or guardian present, a potential breach of police powers.

“I could not believe this was happening to me,” the girl said in a prepared statement read out in the inquiry by counsel assisting the commissioner, Peggy Dwyer. “I could not stop crying. I was completely humiliated.”

The LECC is currently reviewing whether it is legal for officers to force people to squat during a strip-search, a common practice used by police in NSW. In September, the police published a new personal search manual for the first time which allows officers to instruct people to squat, lift their testicles or breasts, or part their buttock cheeks.

In its freedom of information request, the Redfern Legal Centre requested data on the number of women who were forced to squat or lift their breasts during a strip-search, but the information was denied, police said, because the data was “not able to be extracted from the records held”.

“We know from the recent LECC hearings that young women are being asked to squat, and in the LECC case, an officer got on the ground and looked underneath the young woman,” Lee told Guardian Australia.

“How many other young women have been subjected to such concerning police practice?”

In NSW, police are permitted to carry out field strip-searches only if the urgency and seriousness of the situation requires it. In the case of minors, a parent, guardian or support person must be present during the search unless it’s necessary for the safety of the person or to prevent evidence being destroyed.

The LECC inquiry last month heard that some officers did not know their obligation in relation to minors and, in the case of the 16-year-old, there was no justification for initiating the search.

Lee said it was obvious the current legal thresholds were failing to protect young people.

“Young children are particularly vulnerable and at risk of harm from being strip-searched,” she said.

“The current legal thresholds and procedures fail to fully protect children from such harm.

“To protect children the law must be changed to prohibit the strip-searching of children, unless a court order is obtained.”

There has been growing concern about the impact and effectiveness of strip-searches in NSW, particularly in the context of music festivals.

On Friday the NSW coroner will release the long-awaited findings of an inquest into six drug-related deaths at music festivals in the state. During the inquest, a witness described a police officer telling her she would make a strip-search at a music festival “nice and slow” if she did not tell her where she was hiding drugs.

Draft recommendations from the inquiry leaked last month included a call for police to limit the use of strip-searches and scrap the use of drug detection dogs at festivals.

The data obtained by the RLC shows that of the almost 4,000 strip-searches conducted on women since 2016, 66% found nothing. In 28% of the searches, a drug-dog detection was given as the reason for the search.

In a statement, a spokesperson for the NSW police said it was “not appropriate” to comment on the LECC’s inquiry while it was ongoing and did not address questions about the appropriateness of strip-searching 12-year-olds.

However the spokesperson said officers “do not enjoy carrying out strip-searches” but that it is “a power that has been entrusted to us and searches reveal drugs and weapons”.

“People who are trying to hide such items frequently secrete them in private places, and the only way to locate them is by a strip-search, which may involve asking the person to squat,” the police spokesperson said.

The spokesperson said strip searches carried out in public represented “fewer than 1% of the total number of all searches” by police and that 20% of strip-searches are carried out following an indication by a drug detection.

“The use of drug-detection dogs in operational policing is a highly specialised field and NSWPF is committed to ensuring that our training is the best it can be and that the use of drug-detection dogs reflects world’s best practise.

“There are additional safeguards for children and vulnerable people with which police must comply; officers are trained to deal with the public in a respectful and empathetic manner.”