Sex workers in France say their work will become more dangerous if a new law targeting "clients" is enacted.
Prostitutes are fearful that the proposed law, which would see fines of 1,500 euro ($2,000) levelled against those who pay for sex, would force their trade further underground.
The fines would be doubled for repeat offenders.
"Clients will be afraid of arrest, so they will be wanting to take us to places more and more hidden, for example in basements, parking lots, in forests ... isolated places - which we are afraid of, because we won't be secure," Xiao Chuan, a 46-year-old prostitute from China, told the Associated Press.
The draft bill, one of Europe's toughest laws against prostitution and sex trafficking, was presented to parliament on Wednesday, and lawmakers are to discuss the proposal on Friday.
Advocates say it will decriminalise the estimated 40,000 prostitutes in France, by scrapping a 2003 law that bans soliciting on the streets.
But Medecins du Monde, a non-governmental organisation which provides advice, condoms and lubricants to prostitutes, says the law would not protect the country's sex workers.
"They will be forced to continue to hide themselves - because even if they are not risking arrest, their clients are. And their survival depends on their clients," said the group's Tim Leicester.
France has a long history of liberal attitudes towards sex, and other opponents of the bill argue that it intrudes on the private lives of citizens.
"The state has no place legislating on individual sexual activity," philosopher Elisabeth Badinter says.
Hundreds of sex workers protested against the proposal in Paris last month, waving placards reading: "Punishing clients = killing prostitutes" and "We're whores and we're proud", according to the French edition of The Local.
That view was countered by Helene de Rugy, of Amicale du Nid, another group which offers support to sex workers.
"With prostitution, there are no sellers and buyers, only victims and perpetrators," she told The Local.
A report commissioned by the Swedish government showed that the number of people involved in street prostitution in Sweden's three largest cities dropped from around 730 in 1999 to 300-430 a year in the 10 years after a similar law was introduced in 1999.
At the same time, street prostitution in neighbouring Norway and Denmark increased.
The notion of legalised prostitution, as enacted by The Netherlands in 2000, has been criticised as playing into the hands of organised crime and human-traffickers - leading to the further exploitation of already vulnerable women.
Former prostitute Rosen Hicher said targeting the clients is the only way to stop prostitution.
"You need to tackle the root of the evil," she said. "Prostitution is kept up by clients, and the only way reduce it - because of course the mentalities need to evolve - the only way to stop it is to penalise the client."
Guy Geoffroy, president of the special commission of inquiry into prostitution, agreed.
"There is one goal, only one, and that is to drive back prostitution in our country - because prostitution is the domination of one being over another through the use of money, and moreover it has become for many years a manifestation of the scandal of the trafficking of human beings."