At least 3,000 young women in Britain are the victims of forced marriages each year, with the scale of the problem far bigger than originally thought, according to a groundbreaking report out this week.

The first study ever conducted in the UK into the prevalence of the custom shows that there are far more victims, spread across different ethnic minority communities, than official figures suggest.

Teachers should be given a key role in talking confidentially to young girls whom they believe may be at risk of being coerced into marriages, particularly if there is suspicion that an older sister has been married off against her will, the report recommends.

But there also needs to be more determined effort within communities to end the practice, so that forced marriages become a matter of shame and humiliation for parents, instead of being a matter of pride.

The Home Office-funded study calls on authorities to take the institution more seriously, so that it is treated as an issue of illegality, domestic violence and bullying.

The study, which looked at cases in Luton, a town with a large south Asian community, found at least 300 cases where victims had contacted community organisations. Yet the government's forced marriage unit, set up to tackle the problem three years ago, handles only 300 cases a year nationwide.

The report concludes that at least 10 times that number, and possibly far more that, are taking place, without any agencies ever finding out, although forced marriages are illegal under British law.

The government has ordered a national count of missing schoolgirls amid fears that hundreds have been forced into marriage, or are living in fear of so-called "honour" violence.

Researcher Nazia Khanum, who carried out the study, said: "There is this wall of silence around forced marriages.

"Of course, there are thousands of arranged marriages happening in Britain each year but that is very different, as both partners in these are willing participants.

"We are talking about girls being very much coerced into those marriages, often not knowing beforehand who their husbands will be, and then having little or no rights once they are married. Most of them feel there is simply no one they can turn to.'

Labour MP Margaret Moran, who helped set up the study in her constituency of Luton South, said she was shocked by the scale of abuse which they had uncovered. "It's uncomfortable for people to think about, but it can't remain this hidden any longer.

"It's not simply about Muslim families; we also found that it happens among Chinese and African communities too, such as the Somali families. Nor is it something that comes across with new immigrants.

"Many of these women were third-generation British and it is just a custom that is being handed down between the ages. It is something that causes enormous grief and now has to be seen for what it is: a form of bullying, often resulting in violence and great damage."

The report has discovered that sometimes brides are being forced into marriages with men who are severely disabled, and whom they have never met before. There are particular concerns about the women who are brought up outside the UK, are married overseas and then brought into the country as brides.

Many women then find themselves "subjugated into the in-laws' family culture" which can be a traumatic experience.

Some girls are married off when they are just 16, and even if they want to go into higher education, it almost certainly means the end of their schooling.

Shaminder Ubhi, the director of the Ashiana Project, which provides refuge to south Asian, Turkish and Iranian women, said in response to the report: "Certainly we agree that forced marriage, at a basic level, is an abuse of human rights. It can affect girls as young as 14, 15 and 16 years old and can involve emotional coercion, forced imprisonment, violence and in the extreme, murder.

"It is an abuse of women."