IT IS a crowded Thursday night at Motown House in the Roppongi district of Tokyo and the dance floor is heaving with bankers. The bar is hot, but Christina, 20, a Colombian prostitute, is shivering and coughing as she nurses a rum and Coke.

Coughs and colds spread quickly in the cramped living quarters that she shares with four Romanians and three Brazilians. Christina is about to explain the trail of deception and brutality that brought her from family life in Bogotá to Japan when she spots a potential client.

“Got to go,” she shrugs, dragging herself upright and eyeing her Japanese pimp in the corner. “I have to do eight more tonight.”

Christina’s experience is hardly unique. In its annual report on human-trafficking, published this week, the US State Department delivered a damning appraisal of Japan’s national attitude to the issue. Along with Russia, Japan has been placed on the “Tier 2” watchlist, meaning that unless it takes rapid action the world’s second-biggest economy could be on a roster of shame that includes Burma, Sierra Leone and North Korea.

The report refers to Japan’s “thousands of victims of sexual slavery”. Francisco Sierra, the Colombian Ambassador to Japan, said on Monday that 4,000 Colombian women have been trafficked to Japan for sexual exploitation and other purposes. The State Department accepts that Japan is “making significant efforts” to meet minimum international standards, but experts say that the problem is as much cultural as legal.

Jake Adelstein, a panelist at a United Nations conference on human trafficking to be held in Tokyo next week, said: “In a country where there are five or six magazines sold in convenience stores and newsstands that run pages of ads by people wanting to work in the sex industry, the police have a hard time fathoming that there are people in Japan doing this against their will. Work in the sex industry is a regular source of part-time income for a surprisingly large cross-section of Japanese society.”

The number of foreigners held in effective slavery in Japan reflects changing patterns in the sex industry. Japanese men on salaries do not have as much disposable income as they did in the 1980s, and are not prepared to pay the rates charged by Japanese women.

Within the past five years Yakuza gangsters have begun to mine the potential of the Eastern European, Latin American and South-East Asian markets, where women can be procured more cheaply and are easier to exploit.

In a smoky coffee shop in Roppongi, two Hungarian women, in their teens, told The Times how they were lured to Japan. Both are working illegally on tourist visas and live in constant fear of the police.

One said: “Back in Hungary there were people who told us great things about Japan, about jobs where we just had to pour drinks for Japanese businessmen, laugh at their jokes and earn $10,000 (£5,500). When I arrived in Tokyo one year ago, I was met by the agent, who raped me and took my passport and all my documents. I can’t go anywhere, I live in a tiny place and all the money I make has to go straight back to the agent.”

Her friend agreed, describing the threats made against her family in Hungary if she should ever attempt to escape. “The whole thing is run by the Japanese mafia, and they let you know that they have connections around the world. When they say they would hurt my family, I believe them. The Japanese police know everything about it, but do nothing."

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