Schools in Birmingham are refusing to display posters raising awareness of forced marriages because they are "too hard-hitting" and might offend parents, it has been claimed.
A Government survey of councils has found that schools in areas with hundreds of children missing from their rolls object to the notices.
Many others are not even aware of the posters issued by the cross-Whitehall Forced Marriage Unit. All had been singled out for concern by the unit amid warnings that the practice is much more prevalent than has so far been acknowledged.
"In Birmingham, the poster has not been displayed as schools felt that the graphics are too 'hard-hitting'," the Department for Children, Schools and Families (DCSF) said in a memo to the Commons Home Affairs Select Committee.
"Some schools in Leeds are displaying the posters, but others are concerned that they may offend some of their parents."
In Luton, schools and the council have issued cards instead, arguing that they are more discreet and effective than the posters.
It was revealed yesterday that some 2,089 children were "not in receipt of suitable education" across the 15 most worrying local authority areas. Martin Salter MP, a member of the Commons Home Affairs Select Committee which requested the figures, said: "This problem is a tip of the iceberg much, much larger than many people realise. There has been a culture of silence for far too long.
"These figures show that in some places very little progress and in many places insufficient progress has been made in drawing vulnerable young girls' attention to both their legal rights and the support services on offer.
"There are far too many local authorities being lilly-livered about addressing this issue. To me there is nothing more offensive than a young woman forced to spend the rest of her life with someone against her will."
The Government found that "a number of areas" highlighted by the Forced Marriage Unit, including Derby, were not aware of the posters.
A breakdown of the figures on missing children now shows that they include 250 from Birmingham, 520 from Leeds, 121 from Derby and 66 from Luton.
Elsewhere, 294 children are missing in Leicester, 155 from Bristol, 385 from Manchester, 23 from Middlesbrough, 40 from Newham, 16 from Tower Hamlets, 31 from Waltham Forest, six from Blackburn with Darwen and 149 from Lancashire.
It was revealed last week that 33 children could not be accounted for in Bradford.
The DCSF said it was up to schools to decide what posters to display depending on local circumstances but urged them to make such material available.
It said: "We know that some schools have found that other ways of raising awareness are more effective, for example, including teaching on these issues in the curriculum, distributing leaflets or cards, or through enabling young people to access websites. Posters are just one mechanism that can be used to get the message across."
On the figures of children missing from school rolls, the DCSF stressed that they had come to the local authority's attention in "different ways".
It added: "While there is no evidence that large numbers of children who are not receiving a suitable education are at risk of harm, there may of course be some children who fall into this category.
"Local authorities pursue this and take action where they do have concerns about a child, including child protection action, involvement of the police, and involvement of the Forced Marriage Unit where appropriate."