04/03/2014 06:17 GMT | Updated 04/05/2014 06:59 BST

Fewer Young Marriages Are Breaking Down, But the Millions Who Choose Not to Marry Are a Cause for Concern

Divorce rates for young marriages are at a 30-year low, according to the latest figures from the Office for National Statistics. The number of couples breaking up in the first seven years after getting hitched has been steadily decreasing ever since it peaked in 1988 and is now 25 per cent lower than it was then.

At first glance, this might look like encouraging evidence that today's young couples are better than the generation before at surviving the dreaded seven-year itch. Sadly, this view ignores the main cause of the change - the fact that so many more couples now choose to live together long-term without getting married.

While the break-up rate may be falling among the proportion of young people that decide to get married, it is far from clear whether it is also the case for the rapidly growing proportion of unmarried couples in long-term relationships.

In 2012, the latest year for which statistics are available, there were almost three million unmarried people co-habiting in the UK, twice as many as in 1996.

Few would want to bring back the stigma that was once attached to living together outside of marriage, but the problem is that these couples - many of whom have children and effectively share possessions in exactly the same way they would if they were married - have no legal commitment to the relationship whatsoever.

There is a widespread assumption that those living together - particularly those raising a family - have some rights under the law - studies have shown that around one in four people think those living together have the same rights as married couples. In fact, the idea of a 'common-law wife or husband' is a myth, and when a relationship ends or one partner dies, people are often left penniless.

Divorce laws have evolved over hundreds of years to protect vulnerable people who depend on their other half for financial support. A wife or husband who has supported a higher earning spouse throughout a marriage has a legal right to maintenance and 50 per cent of any shared assets when the relationship ends, ensuring they are able to start a stable new life on their own. Judges have free reign to take all the circumstances and history into account in order to ensure a fair division.

Cohabiting couples have no such rights, no matter how long they may have lived together.

In 2007, the Law Commission made recommendations that rights should be given to co-habiting partners when they separate, but so far no changes are in sight.

Of course, cohabitation agreements are available for couples that want to safeguard their rights, but wise though this is, only a small proportion of people choose to put one in place.

It's time for the government to acknowledge the reality of modern relationships and ensure the law keeps pace, otherwise we risk returning to the bad old days when lower-earning partners in a failing relationship were terrified to leave for fear of the life they would face on their own.

James Brown is a partner and family law expert at JMW Solicitors