British police are to work with the authorities in Cambodia to track down sex tourists who travel from the UK to abuse children.
Sex tourists target vulnerable Cambodian children
British officers will also advise their Cambodian counterparts on how to investigate and prosecute offenders.
Work is under way to harmonise the law to allow child sex offenders to be prosecuted in either country.
Police also hope charities working in Cambodia will pass any suspicions about British citizens to the Home Office.
They will help the Cambodian authorities target both sex tourists and British expatriates who exploit children.
The government department has set up a new Child Exploitation and Online Protection Centre to investigate such cases.
BBC crime correspondent Neil Bennett said Cambodia was one of several Asian countries whose poor and vulnerable children were preyed upon by paedophiles.
National Crime Squad deputy director general Jim Gamble told the BBC News website the agreement with Cambodia would prove a model for tackling sex tourism in other countries like Vietnam and Thailand.
He said: "We have identified Cambodia as one of the areas where the local authorities are prepared to work with us.
"People believe mistakenly that they can go there and commit offences and there will be no consequences.
"It is about affecting the sexual predators' thinking. At the moment they think they can go online, find out where is the best place to go and to get a seven or an eight-year-old in Cambodia.
"We have got to make them worry."
Mr Gamble said the new Child Exploitation and Online Protection Centre would see specialist law enforcement officers brought together with lawyers and charities to fight paedophiles.
The agreement with Cambodia and the new centre were the biggest step change in child protection in his 26 years as a police officer, Mr Gamble said.