Postcards have been handed out in Basel, Bern, Geneva, Zurich and Chur – the first four being tournament host cities – urging politeness, respect and cleanliness when paying for sex.

They also call on men to keep their word when paying the agreed amount and remind them that alcohol reduces staying power as well as inhibitions.

Punters can also consult the Don Juan advice centre for information on forced prostitution.

According to the Swiss Aids Federation 230,000 men aged 17-45 pay for sex. Prostitution is legal in Switzerland but prostitutes have to register with city authorities and health authorities and get regular health checks.

Support workers say making kerb-crawling illegal has resulted in the trade becoming more dangerous as prostitutes are forced “underground”.

While the figures cover the whole of last year, Scotpep says that it has become even more dangerous for vice girls since the new law came into force last October.

It comes as latest police figures reveal that a total of 24 suspected kerb-crawlers have been arrested and charged in Scotland’s capital in the first six months since the legislation came into force.

Some prostitutes are said to have turned to handing out a mobile number to potential clients in order to set up meetings. Scotpep believes this new tactic has left women more vulnerable as they are meeting men in more isolated locations.

Ruth Morgan Thomas, Scotpep’s co-ordinator, said: The need for cash to support drug habits has not gone away. Prostitution is being pushed further underground. Women are having to work longer hours and changing the times they work. It makes it harder for us to provide support.

Kerb-crawlers can now face a criminal record and a £1,000 fine.

High-profile police activity has been cited for driving away many men. But those most likely to be violent against prostitutes continue to use their services. Ms Morgan Thomas added: There’s been a decrease in those on the street, but not the number selling sex in the city.