For most of us, the summer holidays are something to look forward to; a time when we can get away from it all and relax. But for some girls from UK diaspora communities, the summer is the beginning of a nightmare, when they return to their home country to visit family, only to find themselves getting married.

The UK government's forced marriage unit, set up to support girls and women at risk, sees double the number of cases reported during the summer holidays. This year the coalition is raising awareness of this by issuing "Marriage: it's your choice" cards, which provide help and information for potential victims, signposting them to confidential advice. We are also reminding young people that they can speak to police or airline staff if they find themselves at an airport with nowhere to turn.

But this isn't a problem that can simply be fixed at UK borders. While our campaign to raise awareness in the UK is necessary, we are also encouraging an international approach to tackle this problem. In the developing world, one in three girls will be married by the time they reach the age of 18, with the highest rates in south Asia and Africa. Girls as young as eight are being forced into marriage, often with men decades older than themselves. The UN predicts that more than 140 million girls will become child brides by 2020 if current rates of early marriage continue.

Girls who are forced into marriage are often trapped in poverty with no means to lift themselves out. These girls are robbed of an education, vulnerable to death in childbirth and at a greater risk of domestic violence and contracting HIV. Early marriage is also inextricably linked with girls suffering domestic abuse and being coerced into sex. Put simply, it endangers life.

Forced marriage will not end overnight; it is a deeply entrenched practice which cuts across religious, cultural and ethnic lines. In many instances, families believe it is in the girl's best interest to be married early, providing her with security and protection. It is not a case of wagging a finger and simply telling people it is wrong. It needs a change in attitudes, beliefs and behaviour.

In the Amhara region of Ethiopia, where half of girls marry before the age of 15, the UK is leading an effort to delay marriage for some 200,000 girls. The Department for International Development's programme there brings together the whole community in a conversation about the risks of and alternatives to early marriage, so that it can begin a process whereby they can reach their own decision to abandon the practice.

There is no single intervention that can end early and forced marriage but education is the most important factor in reducing it. When a girl in the developing world receives seven or more years of education, she will marry on average four years later. She will also have two fewer children. The UK's flagship Girls Education Challenge will ensure that up to one million of the world's poorest girls get a good education.

The good news is that some countries are making progress on reducing child marriage, but progress is slow. Ending child marriage will take time and requires unstinting commitment at community, national and international level. The UK is playing its part but we need others to join so that the rights of millions of girls are no longer violated.