Internet-savvy movie stars Demi Moore and Ashton Kutcher have launched an assault on what they called the “dirty little secret” of women who are traded for sex online.

The Hollywood couple joined with the UN Office on Drugs and Crime to launch a trust fund to help victims of human trafficking, particularly women and children forced into the sex trade.

Ms Moore, star of Ghost and GI Jane, called it “modern day slavery” with an estimated 27 million victims. Mr Kutcher, who has six million Twitter followers, said he wants a trafficking free internet.

He said that about three-quarters of the estimated $32 billion in financial exchanges for trafficking in women and children takes place on the internet.

Prostitution is being forced off the streets and “behind the closed doors of the internet. Behind those closed doors you can make a purchase on the internet and feel completely anonymous,” he said.

“The truth is slavery globally is a dirty little secret. It is happening everywhere, right in front of our eyes and we ignore it.”

“There are more slaves in the world today than ever before in world history.”

Through their Demi and Ashton Foundation the couple have launched an initiative with Twitter, Google, Facebook and Microsoft to put up obstacles to online trafficking.

Ms Moore said the technology would enable investigators to identify and pinpoint the location of those buying sex online.

Ms Moore told how she and Mr Kutcher decided to campaign against trafficking – whether sex slavery, debt bondage or ordinary slavery – after a visit to Cambodia two years ago when they saw girls as young as five who had been forced into prostitution.

“We could not just sit back and not do something about it,” Ms Moore said.

The money from the UN trust fund will be put into giving legal aid and helping rebuild the lives of women and others forced into slavery.