Paris (AFP) - France's upper house of parliament rejected a draft law Tuesday penalising clients of prostitution, as the country wrestles with how to legislate the world's oldest profession.

In December 2013, the lower house of parliament, the National Assembly, approved legislation making clients of prostitutes liable for a fine of 1,500 euros ($1,620) for a first offence and double that thereafter.

But by a large majority, the opposition-dominated Senate reversed the National Assembly's proposal, scrapping the fines for prostitutes' clients and also dropping plans to repeal a law that made soliciting an offence in 2003.

The legislation has already drawn fierce opposition from sex workers, who said it would drive prostitution further underground and make them vulnerable to abuse.

Hundreds of prostitutes -- many South American and Chinese -- took to the streets of Paris on Saturday to protest against the proposed law.

Health Minister Marisol Touraine hit out at the Senate's move, saying: "What happened... is absolutely unbelievable and contemptuous towards women."

Putting the blame on prostitutes rather than their clients is "regressive" and "deprives us of a major tool to reduce demand and therefore prostitution," she added.

Keeping solicitation an offence will "push the women into the shadows and we know it adds to the danger of their situation," said Juliette Meadel, spokeswoman for the ruling Socialists.

Prostitution is legal in France and there are an estimated 30,000 sex workers in the country, more than 80 percent of whom come from abroad. But since 2003 offering sex for sale has been against the law.

According to the interior ministry, most prostitutes are from eastern Europe, Africa, China and South America.

Gregoire Thery, head of a group that urges the complete abolition of prostitution, took aim at the Senate's vote.

"The Senate has chosen to protect the complete impunity of clients and prefers to penalise even further the prostitutes instead of these men," he said.

However, the National Assembly has the last word on the issue and is likely to revert to the original plan of penalising clients.