France has made paying for sex a crime – a radical change of approach in a country where brothels were once legal.

Prostitutes’ pressure groups are divided about the new law. Some welcome the fact that, in future, the clients not the sex-workers will be treated as delinquents.

Other prostitutes demonstrated outside the National Assembly, complaining that they will be forced to work in even greater secrecy and that they will lose their more “respectable” and non-violent customers.

“We will simply face more poverty, more violence and more stigmatisation,” said Morgane Merteuil, spokeswoman for Strass, one of several sex-workers’ unions in France.

The lower house of the French parliament approved the new law at its fourth reading after a three year battle with the upper house or Sénat. In future, anyone who is proved to have paid for sex will face a €1,500 fine, rising to €3,750 for a second offence.

The law also provides financial support for prostitutes who want to create new lives. It will permit foreign sex-workers to remain legally in France, so long as they abandon prostitution.

In pictures: Sex workers protest in Paris Show all 8 1 /8 In pictures: Sex workers protest in Paris In pictures: Sex workers protest in Paris A protester (R) holds a sign reading 'Prostitutes with fists raised against the penalisation of clients!' during a demonstration by sex workers and supporters near the French National Assembly in Paris In pictures: Sex workers protest in Paris A protester wears a hat rimmed with red roses during a demonstration by sex workers and supporters near the French National Assembly in Paris In pictures: Sex workers protest in Paris Sex workers hold signs during a protest against new bill against prostitution and sex trafficking In pictures: Sex workers protest in Paris Transgender sex workers protest against a parliamentary vote to enforce the penalisation of solicitation, near the Assemblee Nationale (French parliament) in Paris In pictures: Sex workers protest in Paris A protester wears a mask during a demonstration by sex workers and supporters near the French National Assembly in Paris In pictures: Sex workers protest in Paris Protesters wear masks during a demonstration by sex workers and supporters near the French National Assembly in Paris, as French lawmakers take part in a final debate on a bill that would make it illegal to pay for sex. French lawmakers were poised on April 6 to pass a controversial law that makes it illegal to pay for sex and imposes fines of up to 3,500 euros ($3,970) on prostitutes' clients In pictures: Sex workers protest in Paris Protesters hold up their fists and chant slogans during a demonstration by sex workers and supporters near the French National Assembly in Paris In pictures: Sex workers protest in Paris Protesters hold a banner reading 'Don't liberate me, I'll take care of it myself!'

A law passed in 2003 which criminalised “passive” street soliciting - in other words wearing skimpy or provocative clothes - was repealed. The estimated 40,000 prostitutes in France, eight out of ten from Africa, Asia or eastern Europe, can now offer their services openly on French streets or on the internet but it will be illegal to approach them.

This is the latest in a series of attempts to regulate prostitution in France since licenced brothels or “maison closes” were abolished in 1946. France becomes, after Sweden, Norway and Iceland, the fourth country in Europe to transfer punishment to the client.

The Socialist deputy who first proposed the law in 2013, Maude Olivier, said the penalisation of customers would “reduce demand” and allow prostitutes to be considered as “victims and not offenders”.

The health minister, Marisol Touraine, said it would “force men to think about what they do and the way they behave”.

Grégoire Théry of the prostitutes’ support group, Mouvement du Nid, said the law would “finally end the impunity of clients”.

Three previous attempts to push through the new law were rejected by the centre-right dominated upper house of the French parliament. The Sénat has now exhausted its constitutional rights of amendment and delay.

The previous French laws on prostitution were similar to those in Britain – and enforced equally patchily. It was illegal to run a brothel or to be a pimp or to solicit in public. It was not actually illegal to sell your body or to buy one.

Under the new law, pimping and brothels remain illegal. It is legal to offer your body for sale but illegal for someone to buy it.

Police unions have campaigned against the changed approach.They say it will be difficult to enforce because financial transactions between prostitute and client will be difficult to prove.