There has been a sharp increase in the number of men seeking help with forced marriages, the government has revealed.

The rise of over 65% in calls from men to the Forced Marriage Unit (FMU) last year is so significant that experts now believe far more British men are being forced into wedlock than had been thought.

"The calls we receive are the tip of the iceberg," said a spokesman for the FMU. "It now seems likely that men account for one in five of all the forced marriages that take place to British citizens."

Men at risk are usually aged from 15 to 24, but the FMU recently received a call to their 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.

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 to take him to India and either kill him, abandon him there or marry him off.

"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."

Last year, the FMU gave advice and support to 1,682 men and women regarding suspected forced marriage. More than 220 calls and emails involved male victims, up from 134 in 2008. As of the end of May this year, there have been 88 calls from men for help.

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

"Boys and men who are forced into marriage find it harder to ask for help than women," said Jeremy Browne, Foreign & Commonwealth 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 report being forced into marriage because they are gay or bisexual, or because their families suspect that they are. But 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, equalities minister.

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 coming into force in 2008, more than 150 orders, which can also be applied for by others acting on their behalf, have been taken out.