Robbie has worked with Unicef in an "ambassador" role

More Precious Than Gold, is described by Williams as "short, but definitely not sweet".

The three-minute movie, which is part of Unicef UK's End Child Exploitation campaign, calls on the government to bring in new laws protect the victims of child trafficking.

It asks for safe houses, counselling and education to be provided across the country.

Parents conned

Williams, who is from Stoke-on-Trent, presents the film and narrates a poem by Simon Armitage.

It describes the buying and selling of young children for sex work, as if they were a crop of exotic fruit.

A Unicef spokesman said: "It is an issue which is slowly coming up as people are starting to realise that this abuse does exist in the UK, not just in Africa.

"A new sexual offences bills is currently going through the House of Commons, but there is a loophole which means that it will still not be illegal to traffic children for domestic labour."

Child trafficking destroys the lives of children David Bull Director of Unicef UK

Thousands of children are believed to be trafficked to the UK every year, mainly from West Africa, Eastern Europe and Asia, and exploited on their arrival.

Children and their families are usually unaware of the real fate the victims are awaiting, and promises about education and a better future are rarely kept.

David Bull, director of Unicef UK, said: "Child trafficking destroys the lives of children.

"Robbie's support will help Unicef to raise public awareness about this child rights abuse and bring it to an end."

Calling for support from his fans, Williams added: "Unicef wants to end child exploitation and are tackling the problem at source, but we need your help.

"I sincerely hope that you join Unicef's campaign to end child exploitation."

More Precious Than Gold was directed by Brian Hill and will be shown on Williams' website and at his European concerts this summer.