French MPs have passed a law making it illegal to pay for sex. Anti-prostitution campaigners have welcomed France's adoption of the 'Nordic model' of dealing with the sex trade, which targets men who buy sex rather than women who sell it. They will face stiff fines of up to £3,000 and will have to undertake classes to learn about the conditions faced by prostitutes.

Christian campaigners are among those thinking that this is a good thing. Christian charity CARE's chief executive Nola Leach said: "Evidence shows that for the vast majority of people prostitution is a harmful and exploitative experience. We believe the best way to protect people is to reduce the demand which underpins prostitution and trafficking."

The move reflects an increasing European consensus that the Nordic model is the way forward. Ireland narrowly failed to pass similar laws before its recent election and the country's Turn Off the Red Light campaign is optimistic it has momentum on its side. The European Parliament voted in favour of the model in 2014 after Labour London MEP Mary Honeyball proposed the motion. She said after the vote: "The idea that prostitution is the 'oldest profession' leads some to think we should accept it as a fact of life – that all we can do is regulate it a little better. This course of action leads to an increase in prostitution levels, normalising the purchase of sex and ingraining the inequalities which sustain the sex industry."

When she says that for most prostitutes the experience is a harmful and exploitative one, Leach certainly has the evidence on her side. CARE cites a 2012 study showing 61 per cent of the women surveyed had experienced violence from buyers of sexual services. It also cites a 2001 survey with 240 women in prostitution in Glasgow and Leeds that found "Half of prostitutes working outdoors and over a quarter of those working indoors reported some form of violence by clients in the past six months."

Does the Nordic model of criminalising the purchase of sex reduce the harm to prostitutes and the incidence of prostitution? According to CARE, it does. CARE told Christian Today that evidence from Sweden and Norway shows street prostitution has decreased, overall prostitution levels are significantly lower than they would be otherwise expected to be and there has been a transformative effect on public attitudes towards paying for sexual services. Furthermore, criticism that this approach would push prostitution underground or make it more dangerous is considered to be unfounded, according to official assessments.

It's fair to say, though, that this view is not universally shared. May-Len Skilbrei and Charlotta Holmstrom in their article The 'Nordic model' of prostitution law is a myth say there's no such thing as one 'Nordic model' as different Scandinavian countries have different rules and migrant women are still targeted by police. The much-touted drop in the number of women working the streets is just because they use mobiles to contact their clients. Furthermore, they say: "Even though surveys among the general public indicate great support for the law, the same material also shows a rather strong support for a criminalisation of sex sellers. This contradicts the idea that the law promotes an ideal of gender equality: instead, the criminalisation of sex buyers seems to influence people to consider the possibility of criminalising sex sellers as well. This rather confounds the idea that the 'Nordic model' successfully shifts the stigma of prostitution from sex sellers to clients." Their view, of course, is also contested.

And alongside enthusiasm for the criminalisation of buyers of sexual services, there's a counter-argument that prostitution ought to be entirely decriminalised. Amnesty International caused an outcry last year when its International Council passed a resolution calling for it to be recognised as a human right. It was widely criticised for its move, with Sweden's foreign minister Margot Wallstrom saying: "It is a myth about the happy prostitute who does this as a free choice. Unfortunately, I can now hear people saying 'hurrah' – all those johns and pimps who run the brothels. It's a multibillion-euro industry."

Advocates of decriminalising prostitution argue that it makes women safer as they can work in safe brothels, get national insurance and healthcare and pay their taxes. It's an attractive argument. But critics point to the experience of women in Germany, where prostitution is legal; there has been a huge increase in trafficking and a fall in the price women could charge for their services.

The truth seems to be that there's no magic bullet that eliminates either the need to sell sex or the desire to buy it. Prostitution is a complex and multi-layered phenomenon. It ranges from women trafficked against their will or forced to sell their bodies to feed a drugs habit, through the hard-up student who occasionally goes home with a rich older man, to 'high-end' courtesans who are happy with what they do because of the lifestyle it buys them. But most prostitutes operate at the dark and violent end of the scale. Many of those who advocate prostitution as a 'human right', or who see it as an extension of a woman's right to choose what to do with her own body, are really only representing the 'acceptable' face of the trade.

Most Christians have a profound moral objection to prostitution, and we need to be honest about this. It's seen as a profanation of something God made holy. We are deeply uncomfortable with the idea of normalising it. However, we can't legislate for morality. The question for lawmakers isn't whether prostitution is right, but how women – who make up the majority of the profession – can be kept safe if they practise it. If decriminalising prostitution could be shown to make women safer and less exploited, it should be decriminalised, but so far the evidence is all the other way. Does criminalising those who purchase sex work, in terms of reducing harm? Evidently, at least up to a point. But the factors that drive people into prostitution – poverty, insecurity, drugs and abusive relationships – haven't gone away. Until society learns better ways of caring for its vulnerable members, this issue won't either.

Follow Mark Woods on Twitter: @RevMarkWoods