2005 data shows that 50.3 per cent of adults in England and Wales were married. Although figures for 2006 are not yet available, the Office for National Statistics says that the steady decline in the number of marriages since 1997 indicates that this figure will now have dipped below half.

More and more couples now prefer to live together, with four million unmarried people now cohabiting in England and Wales.

But cohabiters do not have the same legal rights as married couples and should therefore make sure that they understand what they are legally entitled to.

For example, there can be a lack of financial protection, both presently and in the future, for a partner should the other partner die or the couple separates.

Philippa Pearson, a family lawyer, says: "Many couples who live together believe that they are protected by the law because they consider themselves to be in a 'common law marriage'. But there is no such law and couples have no financial rights if they separate, no matter how long they have lived together or how many children they have had together.

There is also a grey area regarding parental responsibility and if one of the couple dies and there isn't a Will, then the partner has no legal right to the other partner's property. It's always important to get things down in writing to protect yourself in any eventuality."

Here's what you can do to protect yourself legally, whether you've been thinking about living together or you've been together for 20 years.

1. Agree on the payment of your expenses

   Last year the House of Lords ruled that a couple who had lived together for 20 years had to divide the profits from their property according to what they had originally put in. So in case you separate at a later date, it's always wise for you to agree on the financial structure of your relationship.

   If you have bought a property together, decide what you are each going to pay for and how. It may help to separate items into categories, such as:

   • General expenditure (e.g. food, petrol, bills that relate to the occupation of the property, etc.).
   • Mortgage and rent.
   • Bills that relate to the ownership of the property (e.g. council tax and buildings insurance).

   You both may decide that it's only fair to split the costs of the general expenditure, but if one of you has a larger share of ownership in your property, you may consider it fairer to split the bills accordingly (e.g. 30:70 or 60:40 as appropriate).

2. Decide on how you will operate joint accounts or credit cards

   Work out how you will operate the bank accounts that will pay for your expenditure, as this can be crucial to the question of ownership of the property at the end of the day. If you plan to keep your own separate accounts, make it clear that those bills you pay will come from them. Where you plan to have a joint account, agree the amounts you will both contribute and be strict about the items that can be paid from it - if you don't and you buy large items from it, you could find that you have problems agreeing who is to have the item in the event of a split (and the law on this can be quite complex).

   Be careful about credit cards! Nothing can start an argument like one person accusing another of overspending on a joint credit card. Don't go there. Either keep separate cards or if you decide to have a joint one, make sure it's only used for joint purchases and is paid for jointly (and if you do separate, that you agree in advance as to how you will divide these items up - most lawyers advise their clients to toss coins!)

3. Make a cohabitation agreement

   Once you have sorted out all of the financial issues between you, make a cohabitation agreement. You can put it in writing easily by using Lawpack's Cohabitation Agreement Form Pack. This stops you from arguing about these matters again and, should things get nasty at a later date and the dispute ends up in court, the agreement is evidence of both your wishes.

4. Be clear who owns the property

   If you're buying a property together, you must be clear with each other how you are going to own it and what you will each contribute. For instance, if one of you puts down 70 per cent of the deposit, you may agree it's fair that they retain a 70 per cent interest in the property, but only if they then pay 70 per cent of the mortgage each month.

   Whatever figures you agree, make sure that the ownership you want is recorded properly by your conveyancing solicitor who purchases the property on your behalf as tenants in common. If he doesn't do this, then you will own the property as joint tenants, which means that it's owned in equal shares and if one of you dies, the share of the deceased will pass automatically to the surviving partner - not to the deceased's family or anyone else they may choose to nominate in their Will.

   Also, ask your solicitor to draft a trust deed to reflect the agreement you have reached as to what should happen if you separate, since this will then make the terms of ownership absolutely binding upon you both and will cut out any arguments (and huge legal bills) if the unthinkable ever happens.

5. Prepare your Wills together

   If neither of you make Wills, then you both will die 'intestate'. This means that your possessions, finances (and maybe your home) will be distributed according to law (the law of 'intestacy'), which is likely to be against your personal wishes. This usually means that your partner's property would be left to their next of kin (i.e. their parents or even their children), and not you.

   Wills will reflect what you wish to happen to your assets when you die - they are not costly and it's easy to prepare a short Will using a kit such as Lawpack's DIY Last Will & Testament Kit. Not only do they make things clear between the two of you, but also to your respective families - the worst legacy anyone can leave their loved ones is a dispute over their estate when they are gone.

6. Get a parental responsibility agreement

   If you're an unmarried couple and have children who were born before 1 December 2003, then only the mother has automatic parental responsibility. This means that the mother has the right to make decisions regarding the welfare of the children (e.g. medical care and education) without having to consult the father.

   This can cause difficulties if you're a father without parental responsibility and your ex decides to move out of the area, for example, or your partner dies and you have no rights over your children's welfare. If either of these events occurs, then the only way you can gain parental responsibility is by getting a court order or a parental responsibility agreement in your favour.

   Therefore, it's wise to draw up a parental responsibility agreement if you have children; it can be obtained from your local County Court (or from the Court Service's website at http://www.hmcourts-service.gov.uk/).

7. Prepare for future illness

   If one of you gets ill, then it may be difficult for you to decide what happens to your loved one. By creating a Power of Attorney, you can gain control of your partner's finances should they become mentally incapable. Lawpack’s Power of Attorney Kit is a quick, and inexpensive, way to create one.

   If there are certain medical treatments you don't want to receive if you get ill (e.g. whether you would like the life support machine to be turned off), it's also wise to draft up an Advance Medical Decision (also available from Lawpack) stating your wishes. This will help your partner to take care of your wishes, as the hospital may have a duty to consult your partner's next of kin, taking you out of the decision-making process.

Further information
The myth of 'common law marriage'
Your parental rights as an unmarried couple
50:50 split still not assured for unmarried couples
Why should I make a Will?
What are the benefits of creating a Power of Attorney?
Learn more about your rights with Philippa's Unmarried Couples and the Law pocket guide
Buy Lawpack's Cohabitation Agreement
Buy Lawpack's Will Kit
Buy Lawpack's Power of Attorney Kit