Sexual slavery involving boys as young as 10 is being condoned and in many cases protected by authorities in northern Afghanistan.

In a story to be broadcast on Four Corners tonight, the practice of bacha bazi or "boy play", as well as other allegations of child abuse, are explored.

Afghan journalist Najibullah Quraishi has filmed police attending a party where a young boy is the "entertainment". The police shown on the video include one officer from the youth crime squad.

Such parties are illegal under Afghanistan law and with good reason. The "dancing boys" are in effect sex slaves. They are lured off the streets by pimps. They are taught to dance and sing, to wear make-up and to dress like girls. Then they are made to perform before large groups of men. All of them are sexually abused.

Dancing boys are a lucrative business. Powerful former warlords and businessmen love to watch them and will pay a lot of money to have their own boy for bacha bazi. Some of the boys are traded like swap cards among the rich and powerful, and if they disobey their owners they are killed or brutalised.

The trade in boys is well known to the United Nations. According to Nazir Alimy, who compiled a report on the issue for the UN, there is no doubt who is funding this practice and why the police refuse to stop it.

"According to our research these dancing boys are used by powerful men for sex," Mr Alimy said.

Tonight's Four Corners follows the criminal activity of two paedophiles who search for young boys so they can sell or groom them to be trained as dancing boys. In one case the journalist goes in the car with a paedophile named Dastager. As they drive, Dastager describes the type of boy he is looking for. Then in broad daylight the dancing boy master stops the car, goes to a shopfront and brings a boy back to his waiting car.

According to the UN report, there is evidence that the practice of bacha bazi and the sexual abuse of boys is common throughout the north of the country. It confirms that boys, some as young as 10, are lured into life as a sex slave.

There is also evidence this type of abuse is spreading throughout Afghanistan.

Mr Alimy says his research shows it is happening in the south and even in the Afghan capital, Kabul.

"It's true they make the boys wear girls' clothes and make them dance in front of many men," he said.

The powerful men he refers to are often former warlords who helped drive the Taliban out of the north. Others are wealthy businessmen. Under the Taliban, bacha bazi was outlawed. Today it is still a crime, but clearly there is no concerted effort being made to stop the practice and the criminal activity that surrounds it.

Unable to find anyone willing to do anything about the abuse of children, Mr Quraishi flew to New York to meet Radhika Coomaraswamy, who has been appointed by the UN to raise awareness of the plight of children in war zones.

She explains she is deeply pessimistic about the future of these children and the capacity of officials to stop the trade in young boys.

"When I mentioned the topic it was as if I had dropped a big brick, especially in the official circles," she said.

"It was very clear to me, and someone actually said it to me, these are not things people talk about. So let's first deal with the war and then we'll deal with these other issues."

The Warlord's Tune goes to air tonight at 8:30 on ABC1.