British schools were urged to act to protect girls at risk of being taken abroad for marriage during the summer holidays after government figures released on Thursday showed nearly a third of reports of possible forced marriage involved children.

The warning came a day after a mother went on trial in Birmingham accused of tricking her teenage daughter into traveling to Pakistan to marry a much older man to whom she was allegedly betrothed when she was 13.

Campaigners said the case could lead to the country’s first conviction for forced marriage.

Data released by the government’s Forced Marriage Unit (FMU) on Thursday showed it received reports of 1,196 possible cases last year.

Although the figure was 19 per cent down on 2016, it said the drop did not represent a decrease in the prevalence of forced marriage which remained a “hidden crime”.

Nearly a third of cases involved people under 18 - the definition of child marriage. In 15 per cent of cases, the victim was under 16 - the youngest was just two.

More than a third of cases related to Pakistan and more than 10 per cent to Bangladesh.

The biggest change was the rise in reports linked to Somalia, which had doubled since 2016. A fifth of cases overall concerned male victims.

Karma Nirvana, a charity which campaigns against forced marriage, said it had seen a sharp increase in calls to its own helpline.

Charity founder Jasvinder Sanghera said it was alarming that so many cases reported to the FMU involved children and called for schools to take action.

“In Britain today there are children in our classrooms who are either engaged ... at risk of forced marriage or have been forced into marriage,” she said.

“Families will use the summer holidays as an opportunity to take their kids abroad to enter into marriages or engagements - so what are we doing to ensure schools are engaged?”

Sanghera said she had recently met education chiefs to discuss the issue.

“There is still an attitude out there that (schools) don’t see it as a safeguarding issue, but as a cultural issue. They don’t ... want to offend parents,” she added.

Forced marriage is illegal under British law, even if carried out abroad.

The unit could not immediately say if it had referred any cases to police.

“The law is futile if we don’t use it,” Sanghera said. “Many people in Britain, and certainly the victims, don’t even know the law exists.”