Men in some communities are being forced into marriage because their families suspect they are gay or bisexual, the government has revealed.

The Forced Marriage Unit (FMU) says there has been a surge in such cases. Over the past year, the number of calls from men to the unit increased by 65%, from 134 in 2008 to 220 in 2009. Experts believe the figures are only the "tip of the iceberg", as the issue tends to be under-reported for both sexes.

In all, 1,682 forced marriages were reported to the FMU – a joint Home Office/Foreign Office body – last year. Of those, the calls suggest, 14% involved a man being forced into a union. But the unit believes the true figure may be as high as one in five.

Most victims are aged from 15 to 24, but the FMU recently received a call to its helpline from a 62-year-old widower whose family was trying to force him to marry a 35-year-old woman because they no longer wanted to care for him. Cases also include an underaged man taken to Pakistan and forcibly engaged to his five-year-old cousin.

Most calls come from men linked to Pakistan, followed by India and Bangladesh. But it has also received calls from British men with links to the Middle East, Africa and eastern Europe.

According to the FMU, such incidents traditionally increase during the summer, when holidays abroad are taken.

"Professionals and communities can be very intolerant towards men being forced into marriage, even if they have learnt to be sympathetic to women in the same situation," said the spokesman for the FMU. "It can be hard to persuade people to believe it even happens."

"But the threats to these young men are very real. We received a call recently from a young man taken to Pakistan. He didn't know he was going to be married, and when he refused, he was locked in a room. Every day, his father came in to beat him – we're talking broken legs and sexual abuse."

While the vast majority (86%) of victims it sees are female, the FMU says men are being forced into marriage because they are gay or bisexual, or because their families suspect that they are. It can also be a result of family commitments to relatives abroad or their own expectations, securing visas or an attempt to control their son's behaviour or protect a family's reputation.

"This kind of abuse must not be tolerated," said Lynne Featherstone, the equalities minister.

Just two weeks ago, the FMU took a call from a young man living in Leicester whose family had locked him in his bedroom after discovering that he was gay. He told the FMU that his family were downstairs, discussing whether they should take him to India and either kill him, abandon him there or marry him off.

The Albert Kennedy Trust, a charity for homeless lesbian, gay, bisexual and transsexual young people, recently reported a rise in the number of young gay Muslims contacting it for help.

By the end of May, there had been 88 calls to the FMU from men for help. "Boys and men who are forced into marriage find it harder to ask for help than women," said Jeremy Browne, the Foreign Office minister for consular policy. "Of course, women make up the majority of forced marriage victims, and over 1,400 reports of women facing this abuse were dealt with by the FMU last year. But people often don't realise that men can be victims of forced marriage too."

Men and women who have been forced into marriage, or who fear they are about to be forced, can apply for a forced marriage protection order. Since their introduction in 2008, more than 150 orders, which can also be applied for by others acting on a person's behalf, have been taken out.