Thai authorities have now started working with four British detectives to help them curb the problem of child sex tourism.

Officers from the Northumbria force will spend a week setting up a training course for their Thai colleagues and comparing intelligence about British paedophiles in the country.

The four policemen, all of whom have experience of child abuse cases in England, will pass on the latest forensic and interviewing techniques.

They will also use their visit as an opportunity to gain information about more than two dozen British paedophiles thought to be living in Thailand.

In the New Year they will return to Bangkok to run a training course, similar to ones already established in the Philippines and Sri Lanka.

Thai law demands that offenders can only be charged if caught in the act

The move to co-ordinate activities follows the passing of laws in England and Wales allowing courts to prosecute child sex offenders on their return home.

Assistant Chief Constable Tony Crimmens, from Northumbria Constabulary, said the problem is getting their victims to give evidence in a foreign country.

"We see it as a difficult problem - but not an insurmountable one - if that's what we're forced to do," he said. "But we'd prefer to equip the Royal Thai Police with the techniques to deal with paedophiles in the countries where they've committed the offences."

Despite the tougher laws, the United Nations Children's Fund, Unicef, estimates that 250,000 children are bought and sold for sex in Thailand alone.

Some in theThai tourist industry turn a blind eye to child sex industry

Britain is one of the worst offenders when it comes to sex tourism. A British schoolteacher is on trial in the Thai resort of Phuket charged with abusing children as young as seven, and a travel agent was recently jailed in the Philippines.

Thai law demands that offenders be caught in the act before a paedophile can be charged - which makes the police's job much harder. But Thai officers say their British counterparts have been helpful.

Jirapat Labanukrom, of the Royal Thai Police, said the British officers "told us the movements of paedophiles and we'll try and watch them when they arrive".

However, a BBC correspondent says that some in the tourist industry, which plays an increasingly important role in Thailand's economy, still turn a blind eye to those who seek sex with children.