OUR Dirty Dogs Campaign is dedicated to getting dog mess off pavements and out of parks. But if more people trained their dogs to go at home, the problem would stay there. Dogs could go out to the park for fun - to have a run - and leave behind only their footprints.

Most dogs are house- trained as puppies or later in life by new owners. With encouragement, repetition and a lot of newspaper, a habit is formed, and the dog learns not to do it indoors. From house- training it is a small step to teaching the dog to use a particular place. According to animal behaviour experts, this is what dogs want to do: they instinctively prefer to use one spot again and again.

'It is not difficult to teach a dog to go at home,' claims Erica Peachey, an animal behaviour consultant. 'It is simply an extension of house-training. Having taught the puppy not to go in the house, some owners will teach pups that it is not acceptable for them to go anywhere outside, and direct them to a certain place. Dogs are creatures of habit and you build up that habit.'

'We use a system called target-training,' explains John Fisher, founder of the Association of Pet Dog Trainers. 'You take the dog to a specific area, and wait. When it goes, you reward it with something really nice, like a piece of cheese or chicken skin - a little jackpot of reinforcement. A dog will quickly learn that if it goes in the rosebed, it doesn't get anything, but if it goes in the special place at the bottom of the garden, it will be rewarded. It's a stupid dog that doesn't learn that.'

Ms Peachey follows a similar plan: 'Be with the dog when he is about to 'eliminate'. You say the words you always use - guide dogs are taught to be 'Busy'. If you repeat the word a few times, you set up an association in the dog's mind.'

The words do not matter, so long as you are consistent. Writing in 1973, the indomitable Barbara Woodhouse suggested saying ' 'Hurry up', because then nobody knows what you're talking about.' Few would blush today (though many refer, incongruously, to 'toilet- training'). Dr Roger Mugford, an animal psychologist, is more irreverent: 'I used to use the name of a woman prime minister,' he says. 'Now I use the name of a certain RSPCA inspector'.

Experts agree that it is best to train dogs young. But that should not deter the owners of adult dogs. Can an old dog learn new tricks? 'There's absolutely no reason why not,' says Dr Valerie O'Farrell, psychologist and author of Problem Dog. Ms Peachey is also confident of reform: 'All dogs learn all through their lives.' And Mr Fisher says age is no barrier to rapid success: 'It's very, very quick - a matter of days if you put the effort in.'

Mr Fisher has trained his dogs to go on command: 'They know it's not play-time, and that they're not going anywhere until they've done something'. Ms Peachey believes any dog could perform at will. 'It is certainly possible to teach them to go on command,' she says. Dr O'Farrell thinks this may be too tall an order for everyone. But, she says, the problem can be managed by building instinctive behaviour into a reliable routine that allows you to get the dog to the right place by the right time. 'Pay attention to the dog's habits,' she urges. 'It is usually possible to predict 90 per cent of a dog's motions.'

Dr Mugford explains: 'Dogs defecate in association with when they feed. So if you want to catch them at it, you should feed at the same time every day. Lots of people feed in the evening and then complain that the dog shits on the early morning dash round the block. Well, humans eat their largest meal in the evening and go in the morning]'

Of course even with the best trained dog, accidents will happen. 'Teaching a dog to go at home, on command, is not infallible,' says Ms Peachey. 'It's not a substitute for clearing up. Everyone should carry a plastic bag, just in case.'

But the message is clear: dogs of any age can learn to go at home and save the park for walking. 'Teaching the dogs is the easy part,' says Erica Peachey. 'Teaching owners is more difficult.'