British schools have been told to look out for signs of a gruesome form of abuse known as “breast ironing” which involves girls as young as 10 having their chests pounding with heated objects, including rocks, to disguise signs of puberty.

The practice is especially popular in the African nation of Cameroon, where it is intended to protect young girls from unwanted male attention, rape and pregnancy, by keeping them looking like children.

Now campaigners believe the practice is spreading among the several thousand Cameroonians who live in Britain, and are urging schools to look out for signs of the abuse. Speaking to the Sunday Express, Margaret Nyuydzewira of the charity CAME Women’s And Girl’s Development Organisation said: “It is vitally important that people who have a direct involvement with children have an eye on this issue. Children can much more easily open up to teachers, which is why schools must play an important role in raising awareness.”

One victim described the excruciating process involved in breast ironing: “My mother placed a pestle on the fire and then applied it to the two growing breasts on my chest. The process is very painful. She did it over again for about five months.”

The UN has described breast ironing as one of five “forgotten crimes” against women, estimating that up to 3.8 million girls may be affected. As well as causing pain, the procedure can leave girls vulnerable to health problems including cysts, abscesses and infections.

It is believed that one woman has already been arrested in London on suspicion of performing the procedure on her daughter, although she was later release without charge.

Ms Nyuydzewira previously told the Independent that the problem may be more widespread in Britain than people suspect: “Breast ironing is a practice that happens in the privacy of people’s homes so it’s hard to see who is doing it. I am sure it is happening here, but people are not willing to talk about it. It’s like female genital mutilation: you know it’s happening but you’re not going to see it.”

A spokesman for the Department for Education said: “Breast ironing is child abuse and constitutes a crime. We produced updated guidance for schools on keeping children safe from all forms of abuse. The Secretary of State wrote to schools to alert them to this new guidance.”