The French parliament has backed part of a bill that imposes a 1,500 euro (£1,250) fine on anyone paying for sex.
Prostitution is legal in France but pimping and soliciting in public are illegal.
Supporters of the bill say it would punish the customer and protect the prostitute but critics argue it would put sex workers at risk.
Protests for and against the bill took place outside the National Assembly in Paris as the debate took place.
MPs voted for the fine in a show of hands late on Friday night although the full text of the bill – which contains 20 articles – will be put to the vote on 4 December.
Under the new provision, repeat offenders risk a fine of 3,750 euros. Alternatively, they can attend a course to make them aware of the risks involved in the sale of sex.
Most of the bill’s articles are aimed at disrupting foreign pimping networks or helping sex workers who want to stop.
One article aims to decriminalise France’s estimated 40,000 prostitutes by scrapping a 2003 law that bans soliciting on the streets.
The law would instead target the clients.
‘Forced to hide’
The actress Catherine Deneuve is one of hundreds of celebrity figures urging the government to reconsider.
Tim Leicester of the medical charity Medecins du Monde said he feared that penalising those who paid for sex would actually harm prostitutes.
“That won’t change anything for prostitutes. 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,” he told the Associated Press news agency.
Only about 30 members of the National Assembly were present when the debate began on Friday afternoon.
Maud Olivier, the Socialist MP who presented the bill, attacked the “hypocrisy” of critics in her opening speech.
Women’s Rights Minister and government spokeswoman Najat Vallaud-Belkacem told MPs that France was “not a country that welcomes prostitution”.
“The question is not sexuality, we are not there to be moral police… the question is about money that feeds pimping,” she said.
Guy Geoffroy, head of the parliamentary commission created for the bill, also defended the proposition, saying it “advanced women’s rights”.
“We talk about the satisfaction of male desires but what are we doing about female desires?” he asked.
According to the French interior ministry, foreign prostitutes make up 80-90% of all sex workers in the country and most of those are the victims of trafficking rings.