By Subir Bhaumik
BBC correspondent in Calcutta
The government in India's West Bengal State is supporting a programme that offers prostitutes an ancient solution to modern concerns about safe sex.
It doesn't look safe, but experts say it is
"Kama Sutra has many postures that can give men the highest pleasure without consummation and that is what the prostitutes are being taught.
"They are learning something very useful," says Rajyashree Choudhuri, chief of the Institute of International Social Development (IISD),
who designed the project.
Until now, thousands of Calcutta's sex-workers have tried to force customers to use condoms.
Their powerful organisation, Durbar Mahila Samannoy Samity, has decreed that all their members perform safe sex and customers trying to force sex workers to have intercourse without condoms are thrown out of brothels.
Three hour session
But what happens if a customer refuses to use condoms?
The prostitutes lose business, which they can ill afford.
That is a situation the IISD is teaching them to avoid.
In a conference hall in the posh southern locality of Gariahat, the IISD is running its "safe sex" workshop, with backing from the West Bengal Aids Control Society.
Sex-workers from the city's major red light districts are joining up in droves.
"We will back any programme on safe sex. The number of HIV patients in West Bengal is increasing and we want to control it at any cost," says Sachinanda Sarkar, assistant director of the Aids Control Society.
Last year, 1,137 HIV cases were reported in the state. More than 600 cases have been reported this year.
Calcutta prostitutes have become increasingly well organised
Dozens of prostitutes turn up for the workshop and are taken through the voluminous Kama Sutra, India's most famous ancient treatise on sex.
The training lasts for two to three hours.
"They are specifically taught foreplay and other poses that will give men a high degree of pleasure," said Rajyashree Choudhury.
"We teach the girls the art of ensuring a premature but very satisfying discharge by tactfully avoiding intercourse. The Kama Sutra is a treasure house for all that."
A large percentage of HIV/Aids patients in India acquire the virus through unprotected sex.