Under the new provision, buying sex acts will be punishable by a €1,500 ($2,000) fine. Repeat offenders risk a fine of 3,750 euros. Alternatively, a course will be proposed to make them aware of the risks involved in the sale of sex.
Dozens rallied both for and against the bill as debate began in the lower house, the National Assembly, which is expected to vote on the sex bill's
other provisions .
Prostitution is allowed in France, but soliciting, pimping, and the sale of sex by minors are prohibited.
The government says the bill is aimed at preventing violence against women and protecting the large majority of prostitutes who are victims of
But critics warn that it would force sex workers further underground and put them in greater danger, and some argue that everyone should be allowed to
use their own body as they see fit.
Kicking off the debate, Maud Olivier, one of the lawmakers spearheading the bill, blasted the "hypocrisy" of critics.
"One prostitute declares herself free and the slavery of others becomes respectable and acceptable?" the socialist MP asked parliament.
"How can you find glamorous the 10 to 15 penetrations a day endured by prostitutes for economic reasons with dramatic consequences on their health?"
Women's Rights Minister and government spokeswoman Najat Vallaud-Belkacem told lawmakers "France is not a country that welcomes prostitution".
"The question is not sexuality. We are not here to be a moral police... the question is about money that feeds pimping," she said.
The head of the parliamentary commission created for the bill, Guy Geoffroy, 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?" asked Geoffroy, who is from the main opposition UMP party.
As the session got under way, supporters and opponents of the bill rallied outside the parliament.
"You sleep with us and you vote against us," shouted a group of about 150 prostitutes, many of whom wore red or white masks.
"They are trying to stop us from working," said Thierry Schaffauser, an activist from STRASS, France's sex workers' union.
About 50 supporters of the bill, including feminists and others, rallied nearby, holding up a banner reading: "Together for the abolition of prostitution."
There are an estimated 20,000-plus sex workers in France, many from eastern European countries such as Bulgaria and Romania as well as African nations such as Nigeria and Cameroon, and China and South America.
According to the interior ministry, foreign prostitutes make up 80 to 90 percent of all sex workers in France, a vast majority of whom are victims of trafficking rings.
The bill takes inspiration from Sweden, where a similar law punishing clients has reduced street prostitution by half over the past decade.
It also puts forward measures to help prostitutes who want to quit, including foreigners who would be given a six-month, renewable residence permit.
But critics insist that shifting the focus onto clients will only force prostitutes to work even more covertly.
The Greens believe the bill does not make enough of a distinction between victims of prostitution rings and independent sex workers who fear their revenues will fall.
Many of these have taken to the streets in recent days, denouncing a bill that is already scaring clients away.
"I've lost 80 percent of my turnover," Priscilia, a 40-something sex worker in Paris, told AFP recently.
"This law is... killing me," she said, pointing out that one of her clients had told her he now goes to the more discreet Chinese massage parlours.
Some 26 lawmakers from different parties have signed a petition against punishing clients, describing the bill as "a moralistic text".
About 60 people, including celebrities such as actress Catherine Deneuve and singer Charles Aznavour, also released an open letter earlier this month opposing the bill.
Another more contentious letter released last month, entitled "Don't touch my whore!", said: "When parliament gets involved in adopting rules on sexuality, everyone's freedom is threatened."
If approved, the bill will move on to the upper house, the Senate.