Who needs a marriage certificate when they've got love? Without one, warns Elizabeth Heathcote, mothers risk poverty and homelessness
AS AN ACCEPTED way to live and raise children, cohabitation (outside the confines of marriage) has become one of the most widely embraced social changes of the late-twentieth century. After all, when you love each other, who needs a piece of paper?

The answer is, quite a lot of us. It might not be romantic to weigh up such matters in practical terms but the truth is that some people - mostly women - leave themselves extremely vulnerable by not getting married, and usually without realising that they've done so until it's too late. And although the state and the judiciary are catching up with the times, reform may not come for years.

In terms of legal rights, the difference is illustrated most starkly when it comes to separation, and the people most likely to lose out by not being married are those who have compromised their careers, whether to bring up children or nurture the relationship. In the vast majority of cases it will be the female partner who does this, and who becomes the custodial parent after separation. Women in this position all too often subscribe to the myth that since they are considered a "common-law" wife, there's a common law somewhere to protect them. There isn't.

Divorce is governed by the Matrimonial Causes Act which gives the court discretion over the distribution of assets. All property - the home, the pension, income - is viewed as matrimonial regardless of whose name it is in. If the court thinks the wife should have the house which has been bought in her husband's name, it has the power to transfer ownership. If it thinks she's entitled to a share of his salary, she'll get it in maintenance.

The court will base its calculations on a variety of factors including income, the earning capacity of each partner, future earning capacity, contributions to finance, contributions to looking after the home and pension provision. It will then try to work out a settlement that's fair to, and provides for, both parties. If a mother has taken years out of her career to bring up children, or to look after the house and her husband, her earning capacity, now and in the future, and her pension will all have been compromised. The court will try to compensate for that. She may have not paid much towards the mortgage but the court will take the view that she has made a contribution of a different kind.

None of this will happen, however, if you haven't tied the knot. There is no umbrella legislation for unmarried couples, and cases are dealt with piecemeal under property and the Children Act legislation. The basic principle is that you take out of the relationship exactly what you put in, and this is judged wholly in financial terms.

There is no such thing as palimony in this country, no question of an unmarried woman claiming maintenance for herself even if she has sacrificed her entire working life to look after her partner or their children. The house and any other property will be divided according to ownership: in order to get a share each partner will have to show that they have made a financial contribution.

The situation is slightly different if there is a young family but only in the short term. The welfare of dependent children will be the primary concern of the court. Whether you are married or not, it will do all it can to keep a roof over their heads and disrupt them as little as possible. In practice, this tends to mean that, if at all possible, the custodial parent will be allowed to stay in the matrimonial home regardless of which partner owns it.

If the couple are not married, to achieve this the mother will have to apply for a property adjustment order under the Children Act. This transfers the house to her but only temporarily, for as long as the children are minor. After that, it reverts to its original ownership. If the father is paying the mortgage and his name is on the deed, when the children grow up the mother will be out on her ear. If the couple are married, however, the court may well decide that the house should become hers as part of the divorce settlement, or she would be compensated in some other way. "It is very, very different if you're not married," says Markanza Cudby, a family barrister. "There are a lot of sad stories."

Jean Hardy (not her real name) is 32 and lives in Cheshire. She has two children, a baby and a two-year-old, and split up with their father, to whom she wasn't married, a year and half ago, before their youngest child was born. When they'd met previously she had had a well-paid job.

After the birth of her first child she gave up work, reluctantly, because she could not coordinate childcare to fit in with her erratic hours, and so she became a full-time mother. When she broke up with her partner she discovered that she was entitled to no maintenance for herself. He contributes a paltry sum for the children, gathered through the Child Support Agency, and the three of them live in a rented house on income support. "I tried to get another job but it was very difficult to find anything that fitted in with childcare," she says.

She is now doing an access course and hopes to go on and study for a degree which will qualify her for social work, a choice based as much on the needs of her children as on her own desires. It will be years before she completes her education and she sees no possibility of improving her financial situation until then. Her impoverishment isn't just temporary either; she has lost years of pension contributions which will affect her quality of life after retirement.

The situation would be very different if she'd been married. Her husband would have had to support her and, with new legislation on pension splitting, have almost certainly been forced to hand over part of his pension to her. Not marrying is a decision she now regrets. "With hindsight I'd tell anyone, never have children if you're not married," she says. "If you split up you can find yourself in a terrible mess and it can take a long time to dig yourself out."

The anomalies have not gone unnoticed, and neither has the fact that the state is supporting mothers like Jean when, if they were married, their ex-partners would be. But this is an unattractive issue politically; proposed changes are jumped on as being anti-marriage. The Law Commission is working on options for reforming property legislation which could theoretically help mothers after a break-up, but it is at pains to point out that the work is not specifically about cohabiting couples. It is not looking at maintenance or any other related matter, and any changes to the law that it does propose when it publishes its consultation paper later this year are likely to prove controversial and take years to achieve.

Ingrid Davis (not her real name) is not in a position to wait and has been fighting through the courts for six years. She has five children aged between 12 and 20 and split up with their father 10 years ago after 15 years together. He was then a wealthy businessman and they lived in a big house, bought in his name, which she restored. After they split up, the house was sold and, via Children Act legislation, the equity was transferred to a trust through which she bought the family's more modest current home. But when her youngest child is 21, ownership will revert to the father, with whom they have no contact, and she will have to leave. She will receive no compensation for the value she added to the original house or to this one. This is despite the fact that he pays no maintenance for her or the children - the family are surviving on income support. She would like to set up her own interior design and renovation company and support the family herself, but she is not allowed to use the house as collateral.

Her legal battle for a better share continues, but she is pessimistic. "When we went to court we had great hopes," she says. "I spoke for myself and explained my situation, but I came to realise that we couldn't win. Mothers who are unmarried should have equal rights in the eyes of the law with mothers who are married. This is a dinosaur law we are battling against."

It is possible to protect yourself without marrying. You can, for example, negotiate a contract that will give you similar protection to marriage, although this is likely to prove inflexible and will need to be watertight - verbal undertakings are extremely unlikely to stand up in court. But then who wants to negotiate what will happen if you split up at a time when you are falling in love or setting up home together?

Marriage, legally, means you don't have to: it is like a bundle of enforceable rights and responsibilities that will adapt to your changing circumstances and that comes without awkward conversations. The bottom line is that an institution that has been written off by feminists for more than two decades as patriarchal does much to protect the (financially) weaker partner in a relationship - still, usually, the woman.