Figures showing hundreds of pupils from ethnic minorities have disappeared from school have sparked concerns many are being forced into marriages abroad.
From pupil to bride? Hundreds have gone missing from school registers
The figures, on children missing from school registers in England, were reported to an MPs' select committee.
The MPs have called for more investigation into the statistics.
While the government's Forced Marriage Unit sees 300 cases in the UK annually, a separate study records 300 reports each year in the town of Luton alone.
While precise figures are difficult to obtain, the author of the Home Office-funded Luton study said the statistics available almost certainly represented the "tip of the iceberg".
Management consultant Dr Nazia Khanum said if one assumed reporting levels in rape and domestic violence cases - at around 10-12% - were similar to reporting levels in forced marriages, it could be concluded that there were about 3,000 forced marriages a year in the UK.
Dr Khanum, whose report is being published on Monday, said although the figures were estimates, "it still indicates the scale of the problem of forced marriages, which are unacceptable, and condemned by all religions".
Forced marriages are not the same as arranged marriages, in which both parties consent.
Dr Khanum added: "Forced marriage ... is a part of a patriarchal system where parents believe they know what is best for their children."
In its separate probe, the Home Affairs Select Committee has called for more investigation into the figures it obtained on children missing from school registers.
Some MPs said they suspected young girls, and occasionally boys, were being taken out of education and forced to marry against their will - often because they were deemed to have become too Westernised.
Chairman of the committee Keith Vaz MP said 33 children were missing from schools in the Bradford area, and other pupils were unaccounted for in a further 14 local authority areas that reported to the committee.
Mr Vaz told BBC Radio Four's Today programme as many as 500 young people could be unaccounted for.
"Whether or not they have subsequently been taken abroad and been subjected to forced marriages is a separate issue.
"But I think what the committee would like to do is to follow the children. Find out what the local authority has done and then pursue it."
He said the MPs had asked the Foreign Office to make available their entry clearance manager in Islamabad, Pakistan, to give evidence to the committee, so they could determine if that was where some of the pupils had gone.
Education officials have a statutory duty to inform social services if there is no good reason for long-term school absence.
The councils that provided the figures said it was unlikely the missing youngsters were forced into marriages.
But government officials have been told to "dig deeper" into the data..
One teenage Pakistani girl told the BBC how she was pulled out of school when she was just 13, taken to Pakistan and forced to marry a man who assaulted, abused and raped her.
She said she prayed someone back in England would report her disappearance and come looking for her but nothing happened.
"I think they let me down", she said.
"I did still secretly think when I was in Pakistan, the school might search for me. Nobody looked for me. It was horrific."
Having returned to the UK to have a baby, she is now in hiding after her husband followed her from Pakistan.
If you know anyone who may be forced into marriage overseas, you can call the government's Forced Marriage Unit on 020 7008 0151. From outside the UK, dial +44 20 7008 0151.
All calls are treated in confidence.