Last Monday, James Martin was sentenced to four and a half years in jail for killing Stella Frew. They had argued in his van, then he accelerated away with her hanging off its side, eventually running Frew over, causing her catastrophic injuries. Martin sped away with her handbag in the van, which he later dumped.

The cause of their altercation? Martin refused to pay her for the sex act she had just performed on him. Like many women who sell sex, Frew struggled with drug and alcohol addiction and was under their influence when she approached Martin. Her daughter described her for the court as the “kindest, most warm-hearted woman” who had been abused and hurt by men her whole life. The judge commented that Martin had shown barely any empathy for his victim.

And so it has always been. Prostitution is laced with mortal peril: women who sell sex are 18 times more likely to be murdered than women who don’t, according to one study. Yet these women have throughout history been cast as second-class citizens, not worthy of the same concern as other victims.

How best to prevent violence against those selling sex, the vast majority of whom are women, is a question that has long divided feminists. For some, it is about decriminalising the selling and buying of sex, which in England and Wales would mean dropping criminal offences such as kerb crawling, soliciting and running a brothel. There will always be prostitution, so the argument goes, so best to keep it out in the open. Others agree that the selling of sex should be decriminalised in all circumstances and think women should be provided with ample support to get out of prostitution, but argue that the buying of sex, an almost exclusively male activity, should always be a crime.

The full decriminalisation argument is driven by a belief that it is possible to sufficiently strengthen the agency of those who sell sex to transform it into “sex work”, like any other job. You can see what makes it an appealing frame, powered by an archetype that has evolved from the Pretty Woman male saviour narrative, to the sex-positive woman sticking two fingers up at a socially conservative society by making bags of money doing something she loves. Sex work is a choice that should be respected and we should destigmatise it by decriminalising the men who buy it and regulate it to make it safer. Women railing against this are depicted as prudes constrained by their own squeamishness about sex.

There are two reality checks that bring these theoretical arguments crashing down to earth. The first is that for every woman or man selling sex who regards it as a positive choice, and there are some, there are many more who have been trafficked or exploited and are effectively enslaved to criminal networks, working for a pittance, or for drugs to forget the trauma of being forced into selling yourself to be penetrated again and again, or for nothing at all.

In one investigation into sex trafficking, Leicestershire police reported that 86% of the women in brothels they visited were Romanian; in Northumbria, it was 75%. Numerous studies have shown just how dangerous prostitution is: a majority of women selling sex have experienced severe and repeated violence, with more than two-thirds suffering from PTSD at levels comparable to war veterans. Women who are actually or effectively being forced into selling sex have little voice in policy debates, although there are prominent survivor networks that argue for abolition.

Second, as the feminist campaigner Julie Bindel exposed in her 2017 book The Pimping of Prostitution, decriminalisation and regulation has not been the success its advocates claim. Bindel visited and interviewed women working in legal brothels in the Netherlands, Germany, Nevada, New Zealand and Australia and found exploitation to be rife, with legalisation acting to empower brothel owners. In one Las Vegas brothel, women weren’t allowed out unaccompanied or without their manager’s permission. In a German brothel, women had to service six men a day at the minimum rate just to make back the room rent. In a New Zealand brothel, women said men could simply complain to the manager and get their money back, leaving them with nothing.

Decriminalisation increases the overall extent of prostitution in a country without decreasing its harms or delivering any of the promised benefits of regulation. In New Zealand, Bindel revealed there were only 11 brothel health and safety inspections over a 12-year period. And decriminalisation makes it even harder for the police to combat trafficking; Spanish police describe how difficult it is to investigate when they enter a brothel and clearly frightened and distressed young women tell them they are working there by choice.

Decriminalisation can’t make prostitution safe because it is inherently dangerous and exploitative. How is a woman selling sex supposed to maintain safe boundaries or withdraw consent when a man physically capable of killing her is hurting her?

The men who buy sex all too often escape scrutiny. The Invisible Men project documents the nauseating way men talk online about their experience of women selling sex, very little of it printable. Research finds that men who buy sex are also more likely to abuse their partners, have a stronger preference for impersonal sex and to commit rape and other sex offences.

Correlation may not equal causation, but it’s not hard to imagine how using women for a price, even if it hurts them, further hardens already toxic attitudes towards women. These men have a vested interest in the sanitisation of their sex-buying. Perhaps the most extraordinary example is the former MP Keith Vaz, who chaired a home affairs select committee inquiry that came down against criminalising those who buy sex, and who a few months later was exposed as having offered to buy cocaine for two men selling sex.

There should be zero stigma, only help and support for those caught up in prostitution. But we legitimise the men who engage in the harmful practice of buying sex to our detriment. In the UK, it is estimated about one in 10 men have paid for sex; in Spain, where it is decriminalised, it is much higher. To accept that prostitution is always going to happen, and therefore the best we can do is regulate it, not only means tolerating the abuse of women: it is to be complicit in its expansion.