In a quiet suburban house on the outskirts of a city in northern England, Maureen* – a mother of two in her late 30s – sits cradling a large dark stone in the palm of her hand.

She had just been using it to crush spices for a family meal. But a few years ago, she was using it for a very different purpose.

She heated the stone and then pressed against the chest of her eight-year-old daughter. She stopped only when her daughter cried out in pain and the heat from the stone had left a bruise on the child’s body.

“When they [police] asked me why I did it, I said to them: it’s a tradition,” Maureen explains, recalling her interrogation as bewildered social workers googled “breast-ironing” on the internet.

The practice is aimed at slowing physical maturity in girls to spare them the unwanted attention and predation of young men while they are still minors. But doctors say it does little to delay breast development, and threatens all kinds of physical and psychological harm.

The intervention is not confined to this city. A Guardian investigation heard anecdotal evidence of dozens of cases in London, Leeds, Essex and Wolverhampton.

Yet British authorities, social workers and some NGOs appear to be unaware or in denial that the practice exists in the UK and are not taking a proactive approach to find or even keep track of the cases.

Police say the obvious problem is that children are unlikely to report their parents, and few other people will ever get to know it is going on.

A parent in Cameroon heats a stone to iron the breasts of her daughters. Photograph: Veronique de Viguerie/Getty Images

“What we wouldn’t expect is a victim to necessarily walk into a police station and report what is happening to them,” says Allen Davis, the Metropolitan police’s lead on illegal culture practice. “If people were to tell us where it’s happening, when, to whom and by whom – then we will do something about it.”

“Like FGM, cultural practices that harm children or adults are complex issues to solve,” says Jess Phillips, the MP for Birmingham Yardley. “However, we must do all we can to educate communities against the practices and seek to prosecute perpetrators and protect victims.”

Maureen says that having had her own breast ironed when she was a child in Cameroon, she became convinced this would help her protect her own daughter from harm, especially when she noticed her beginning to develop.

“The area where we were living – it wasn’t a good area,” she says, describing youth gangs walking the streets, fighting and peddling cannabis. “I couldn’t let her play outside.

“When you saw her, you couldn’t see the baby in her – you just saw a teenager. So for me it was really a nightmare.”

Maureen called her mother in Cameroon, who guided her through the process.

“Some women say that they do [it] because these girls … are prone to rape,” says Mary*, a local community activist in south London.

“We have chat groups most weeks and women have talked about breast-ironing,” says Karyne Tazi, the executive director of the Women & Families Resource Centre in Wolverhampton, who works to educate women on the risks of the practice.

“You’re thinking about it like a vaccine: ‘It’s painful but it helps,’” says Tazi, adding that the practice has serious physical, psychological and overall health effects that many people are simply not aware about.

Jennifer Miraj, a nurse, recalls seeing dozens of cases of women and girls who had been breast-ironed while she worked in hospitals around the UK.

She says she saw “women who couldn’t breastfeed and had long-term issues with cysts and infections from the milk ducts not being able to express the little milk they were producing”.

She says many women had “painful red infections and no opportunity to bond [with the baby] by breastfeeding”, and that it was common for women who had been breast-ironed to be diagnosed with breast cancer.

Cathy Aba Fouda, who was subjected to breast-ironing in Cameroon, where the practice is thought to originate, also says that there have been cases of women who had been breast-ironed developing breast cancer.

“We lost a young woman only last month who had been breast-ironed as a girl and died from breast cancer, aged just 24,” says Fouda. “I don’t know why no one has done a study on the link between the two.”

Psychological problems are also very common following breast-ironing and can last for years, according to Fouda. “When I had a baby, all the trauma came flooding back,” she says, explaining that whenever the child reached for her chest, she felt panic like someone was about to hurt her.

Yet some UK-based community activists appear to be unaware of the risks.

“I haven’t seen any research which said that breast-ironing is bad,” says Mary, adding that some women say it improves the mother-daughter bond. “Up to now I haven’t heard that it’s related to cancer.”

“The only thing is that the nipple sort of goes into inverse, and it makes it very difficult if you have to breastfeed.”

“FGM, breast-ironing – it fundamentally comes back to the control over women’s bodies,” says the anti-FGM activist Leyla Hussein, who also provides therapy to breast-ironing survivors.

“The whole community needs an education,” says Mary Stella in Wolverhampton. “Because we are coming from a background where we think it’s OK.”

Nazir Afzal, a former chief prosecutor for north-west England, says that introducing a specific law against breast-ironing could help, citing a similar experience with the criminalisation of forced marriage. “Sometimes you need to change a law to send out a message,” he says.

But others believe this would spell disaster and would push the practice even further underground. “Look at FGM: from 1985 till now they are still looking for somebody to prosecute – is that not ridiculous?” says Mary.

“Going around in a sympathetic way saying: ‘Do you know anyone undergoing this?’ so that they can latch on to that child like a tonne of bricks – that’s not support, is it?”

Tazi says interventions need to be subtle. “More organisations need to have the resources and opportunities to get these communities to talk. Because if they don’t talk, it will always be an underground crime … But the more people talk about it, the more we’ll find solutions.

“When we first started, you hold a chat group on breast-ironing and labia pulling and no one would turn up. But they’ve seen us: we’re there, we’re constant, we try to work with them around it, not criminalise them. And they’re now more open to talking,” says Tazi.

In Maureen’s case, her daughter was held by social services for 10 days before being released back to her family. Maureen faced no criminal charges, only a police caution.

“A social worker would come around once a week for one or two months, that’s all. After then, they just dropped the case,” she says. Maureen moved her daughter to another school.

“If I knew the laws of this country, I should’ve kept my daughter at home for three days [instead of sending her to school],” she says, slapping her hands together in frustration.

“Until that bruise just went away. They [would] never have known.”

* Name changed