The writing has been on the wall for parts of Amsterdam's red light district ever since the city's mayor, Job Cohen, pledged to clean up the downtown back streets, swapping seediness for sophistication and replacing the neon lights and window prostitutes with stylish shops and eateries.

"There's just too much sex in this part of the city, " Cohen said. The mayor denies wanting to rid Amsterdam of prostitution altogether . . . a move which would create huge headaches for tourism authorities, as well as denting the city's revenues. But he is concerned the surfeit of sleaziness is turning the area into a mecca of drug dealing and petty crime.

"It is not about chasing prostitution of the Wallen, " the mayor said. "What we do want is to get rid of the underlying criminality."

The city, under pressure from Cohen, refused to renew the brothel operating licences of 'Fat' Charlie Geerts, one of Holland's wealthiest sex bosses. Geerts launched an appeal over the licence renewals but when that failed he agreed to sell the properties to a municipal housing association, giving a legal undertaking not to invest any of the proceeds of the sale in "sensitive" ventures such as other sex businesses, soft drugs dens (coffee shops) or gambling halls.

However, the Dutch sex workers' union has criticised the plans for "lights out" in a third of brothels' windows where women show off their wares, paying 100 for half a day in rent. "The more brothels there are, the less exploitation there is, " a spokeswoman, Metje Blaak, said. "Cohen is playing into the hands of exploitation. Because the women. . . will go and work somewhere we can't get to them. You're just sending them deeper into the woods." That would make it more dangerous for the women in terms of their personal safety and more difficult to halt the spread of STIs.

Political opponents accuse Cohen's administration of being prudish. They say the mayor was behind a ban on public nudity during the city's annual Gay Pride festival.

Successive surveys have shown that the abolition of the general ban on brothels in 2000 has not improved the position of prostitutes in the Netherlands, as was hoped.

The mayor hinted this week that more restrictions might be on their way.

"The legalisation of prostitution did not bring about what many had hoped, " he said. "We are still faced with distressing situations in which women are being exploited. It is high time for a thorough evaluation of the prostitution act."