An African practice of “ironing” a girl’s chest with a hot stone to delay breast formation is spreading in the UK, with anecdotal evidence of dozens of recent cases, a Guardian investigation has established.

Community workers in London, Yorkshire, Essex and the West Midlands have told the Guardian of cases in which pre-teen girls from the diaspora of several African countries are subjected to the painful, abusive and ultimately futile practice.

Margaret Nyuydzewira, head of the diaspora group the Came Women and Girls Development Organisation (Cawogido), estimated that at least 1,000 women and girls in the UK had been subjected to the intervention. There has been no systematic study or formal data collection exercise.

Margaret Nyuydzewira, who herself was subjected to the practice of breast-ironing as a young woman. Photograph: Inna Lazareva

Another community activist, who did not wish to be named, said she was aware of 15-20 recent cases in Croydon alone.

“It’s usually done in the UK, not abroad like female genital mutilation (FGM),” she said, describing a practice whereby mothers, aunties or grandmothers use a hot stone to massage across the breast repeatedly in order to “break the tissue” and slow its growth.

“Sometimes they do it once a week, or once every two weeks, depending on how it comes back,” she added.

The perpetrators, usually mothers, consider it a traditional measure which protects girls from unwanted male attention, sexual harassment and rape. Medical experts and victims regard it as child abuse which could lead to physical and psychological scars, infections, inability to breastfeed, deformities and breast cancer.

The United Nations describes it as one of five global under-reported crimes relating to gender-based violence.

One woman living in the suburbs of an English city told the Guardian how she went about ironing her daughter’s chest at the first sign of puberty.

“I took the stone, I warmed it, and then I started massaging [my daughter’s chest],” she said. “And the stone was a little bit hot. When I started massaging, she said: ‘Mummy, it’s hot!’” The child developed bruising and the mother was eventually questioned by police, before being released with a caution.

British-Somali anti-FGM campaigner and psychotherapist Leyla Hussein said she has spoken to five women in her north London clinic who had been victims of breast-ironing.

“They were all British women, all British citizens,” Hussein said. One of the women said she became flat-chested as a result of the practice, said Hussein. “She kept saying: ‘I have a boy’s chest.’ But no one has ever questioned her about it. No one had physically checked her. This was in north London, just down the road,” said Hussein.

“I was a nurse in the UK for over 10 years and watched the numbers grow,” said Jennifer Miraj, who worked in hospitals in Essex, Glasgow, Birmingham and London until 2015. Miraj said she came across confirmed cases of breast-ironing in approximately 15 adults and eight girls.

“I took care of a young 10-year-old girl who had an infection, which had been going on for a few years from ironing,” she said, describing a case from Broomfield hospital in Essex.

Mary Claire, a church minister in Wolverhampton, said she had spoken to four victims in Leeds, originally from west Africa. “You could see the marks,” she said.

Police say they have fielded no allegations about breast-ironing in the UK, but suspect it is happening.

“If I knew it was happening, I would do something about it,” said the Insp Allen Davis from the Met police.

“Prosecutions are really important,” he added. “People have to recognise these practices for what they are – child abuse.”

A recent London borough of Brent mental health report mentioned that voluntary sector organisations working across the African diaspora felt that breast-ironing was “an emerging issue” which “was not receiving enough attention”.

“It is surprising to me that the police and other authorities are not allocating even the resources clearly needed to deal with this horrific phenomenon,” said Alex Carlile, one of UK’s leading QCs, who is a former deputy high court judge and a member of the House of Lords.

“Surely it’s high time for the police and prosecuting authorities to address and tackle the issue in a robust manner, sensitive to the personal issues that arise for young victims and their communities.”

“It’s not only an issue of funding, it is also an issue of political will to tackle something that historically has been accepted as a cultural practice,” said Conservative MP Maria Miller, who also chairs the women’s and equalities select committee in parliament.

“I think public service providers have to start being more honest and realistic about some of the things they are encountering, and to have the support to challenge what are abusive and barbaric practices, particularly aimed against children,” she added.

The government has said it is “absolutely committed” to stamping out the practice. But activists and social workers say that little has been done thus far.

“Nothing came out of this – nothing!” said campaigner Geraldine Yenwo of Cawogido. “We talk about early marriage and violence against women and girls but no one ever mentions breast-ironing,” she added.

Nyuydzewira, who was herself subjected to the abuse as a girl, said British authorities were not taking the problem seriously, and have not prosecuted those doing breast-ironing on their children on grounds of it being seen as a “cultural practice”.

“The British people are so polite in the sense that when they see something like that, they think of cultural sensitivities,” she said. “But if it’s a cultural practice that is harming children … any harm that is done to a little girl, whether in public or in secrecy, that person should be held accountable.”