The document also provides guidance to doctors, police, social workers and other community workers.
Foreign Office minister Chris Bryant told the BBC that professionals needed to have their "eyes wide open".
"There are key times of the year, particularly if an elder sibling has married very young or suddenly left school, if a youngster is self-harming or if they are constantly being accompanied by parents, even to a doctor's surgery," he told Radio 4's Today programme. "These may be clear signs that there is a problem."
"I should make it absolutely clear there is no culture and there is no religion in which forced marriage should be acceptable or indeed is acceptable," he added.
"I know there are maybe some people who think this is an issue about Islam - it's not. Islam does not recommend or accept forced marriage. Marriage in every religion has to be freely and openly consented to."
However, according to separate research for the government, also published on Thursday, some local bodies are not doing enough to intervene.
Mayah: "I was very much sedated, I was beaten up, I was locked in"
The report for the Department for Children, Schools and Families details criticisms of some schools and education authorities.
Critics say some are "non-responsive" and failing to intervene as they dismiss forced marriage as a "cultural issue" or fear a backlash from powerful figures in minority communities.
"In all areas we noted a variation among key partners in the importance they attached to responding to forced marriage," says the report.
"One respondent talked about how it was precisely those cases of children [going missing from education] that showed the signs of forced marriage that were less likely to be followed up in schools as this was seen as an issue specific to the culture of the child."
Jasvinder Sanghera of Karma Nirvana, a national campaign group against forced marriages, urged public sector workers, and particularly teachers, to act on suspicions.
"This is not something you must be culturally sensitive about," she said. "This is a child abuse issue, and you must treat it in that way and follow your child protection procedures. Do not turn a blind eye".
The Forced Marriage Unit, run jointly by the Home Office and Foreign Office, received 1,600 reports last year - and intervened in 420 actual cases.
Overall, there are estimated to be at least 5,000 cases of forced marriage, but it is impossible to know for certain.
In some cases, a specialist British team launched secret rescue missions to repatriate victims held captive by their families abroad.
The courts have also made 36 forced marriage prevention orders, a recently created power designed to prevent people being taken abroad against their will.
Read some of your comments so far below.
As a retired UK teacher with many years' experience in London schools I think this is an excellent initiative. I have had two students fail to return from trips abroad after the summer holidays and have often wondered about their fate. Remember the child is still a child and may be reluctant/fearful to talk about the issue in school. It is a form of child abuse and teachers need to be trained to spot the symptoms and follow clearly defined procedures.
Ian Hollingworth, Pakkred, Thailand
I am a student and I don't agree with forced marriages. But there should be advertisements on billboards, leaflets given out to students, so young people know whom to contact for help. Forced marriages take place more often once a daughter or son come to leave college at the end of each year.
Rameez Riaz, UK
I've worked as a medical professional in Pakistani areas and find forced marriages are still commonplace. A sad state of affairs, especially as it's now the second generation who still uphold this abhorrent tradition. Areas such as Bradford and Nelson in Lancashire are full of women forced either physically or emotionally into marriages against their will.
A Mahfooz, UK
Saying forced marriage is 'totally unacceptable' backed up by little more than a severe 'tsk tsking' is going to achieve very little. We should view the practice as an irrefutable sign that those responsible have rejected our culture and repatriate them to their country of ethnic origin.
Andy, Warwick, UK
This has two responses, either it is yet another example of religious dogma hiding behind cultural difference blighting humanity and maintaining sexism; an issue which western society seems reluctant to address. While the second response, takes the culture line, that this is a clash of cultures; but again is an issue the west is reluctant to address.
Andy Rogers, Lancaster, UK
In Bangladesh , Pakistan and India some families are still not giving daughters and sons their right to choose. It simply creates bitterness, true frustration, hatred and deep anger for a lifetime. Parents never admit or confess the mistakes and the complications they have created for their children's lives.
Moon Ahsan , Dhaka, Bangladesh
From the report it is apparent that parents need to change their 19th century mindset. So, why not have these (all) parents undergo re-education at their children's school during holidays? Their absence from school would give the first clue that they are planning forced marriage of their children.
Sid, Delhi, India
Forced marriages are not a "cultural issue" as assumed by many. It is more of a moral issue where the victim is no more than a kid being forced into a marriage mainly because of the fact that he or she is a Brit. Their spouses then could come into the UK and work freely.
Sainagakishore Srikantham, Pune, India
The underlying reason for forced marriages abroad is the conservative mental framework of the migrants who migrated to European countries. Those migrants have not been able to adapt to the code and living standards of UK society.
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