The scent of perfume hangs heavily in the air as two Asian businessmen take their seats in a dimly lit nightclub. Soon a ring of attractive young Vietnamese women forms in front of them. An older woman uses a flashlight to show each of the eight girls in turn in the darkness. Each man chooses one each to join them for the evening, and the rest go back to join the other 100 or so women in the bar's entrance area, waiting for customers. It is just business as usual at one of the biggest hotels in Hanoi, despite the latest well-publicised crackdown on prostitution by the Vietnamese government, whose seat of power is just a few kilometres away. Early this month, state-run newspapers reported that as many as 10 large Hanoi hotels were under investigation for allowing prostitution activities. Late last month, Prime Minister Pham Van Khai ordered a temporary ban on new bars and karaoke outlets, hundreds of which act as venues for the sex trade in Hanoi alone. And about the same time actress Dinh Thoai Yen Vy was reportedly sent to a rehabilitation centre after authorities said she was part of a high-priced prostitution ring. The crackdown, expected to continue for at least two more months, comes during the run-up to next year's 10th Communist Party congress. Vietnam will choose its leaders and set its major policies for the next five years in the months leading up to the congress. Vietnam analyst Carl Thayer, calling it the 'political season', believes the timing is no coincidence. 'Cleaning up social vices is a way of enhancing one's political credentials or a way of indirectly attacking an incumbent for failure to deal with this issue,' says Professor Thayer, from the Australian Defence Force Academy. In Vietnam, prostitution is grouped with other societal problems such as drug use as 'social evils'. As such, the communist authorities officially take a hard line against it. But at street level the sex trade is rife, and no secret to the public. Nguyen Vi Hung, head of Hanoi's anti-social-evils department, estimates there are 2,000 sex workers in the capital, but the real number of women who accept money for sex on some basis is believed to be far higher. 'It's a very difficult task to confirm someone is a prostitute,' Mr Hung says. No hard data exists on whether the sex trade is growing, but the common belief is that it is. Wealth is spreading through the fast-developing country, and girls from impoverished rural areas are solicited into the trade in the cities. Mr Hung estimates 70 per cent of Hanoi's sex workers are from outside the city. Observers believe the latest crackdown is unlikely to curb the practice for long. The posturing by the Communist Party is up against not just cultural norms and economic forces but also corruption - many sex-trade outlets pay the local police to look the other way.