It's time for our prostitution laws to change. This International Women's Day, let's call for changes to prostitution laws so vulnerable women are afforded better protection.

The best way to do this is criminalise the purchase of sex so the burden of blame falls most strongly on the buyer, not the seller.

While prostitution has been called the 'oldest profession in the world', a more accurate description is to call it one of the most exploitative. It is an enduring form of exploitation that creates a radical power imbalance between the buyer and the seller.

While there are some men in prostitution, the vast majority are women. Contrary to the rhetoric of some pro-prostitution campaign groups, the evidence tells us that the majority are not there out of a positive choice. Indeed, many are in prostitution because of a lack of choice.

When you listen to women who have lived through prostitution, the stories they tell are a powerful rebuke to our society. They speak of women being treated as mere commodities, as objects. They speak of women who felt they had no choice but to sell their bodies for sex in order to survive. What a contrast to the glamorous images of prostitution that still exist in fiction and sadly even on TV.

One survivor, Rachel Moran has written about her own experience. She had this to say: 'I pay no respect or accommodation to the glamourising or sensationalising of prostitution. These are not true depictions of prostitution... My assessment of prostitution and my opinions of it I take from the years I spent enduring it and everything I saw, heard, felt or witnessed or otherwise experienced at that time. There was no glamour there. Not even the flicker of it. Not for any of us.'

Why do people, and especially women, end up in prostitution? Of course each person is different but research indicates that circumstances such as homelessness, debt, problems with drug or alcohol use and a childhood in local authority care often feature in the stories of people engaged in prostitution. However they come to enter prostitution, the evidence also tells us that it involves serious risks of harm to people's health and wellbeing.

Consider, for example, research produced for the Scottish government at the end of 2016. It reported that 'most respondents who provide services and support to those involved in prostitution emphasised a range of risks and adverse impacts associated with prostitution in the short and longer term in relation to general and mental health, safety and wellbeing and sexual health'. Other studies have revealed that women in prostitution are more at risk of sexually transmitted infections. In one survey 61 per cent of the women surveyed had experienced violence from buyers of sexual services.

God created people for purpose, not purchase. No one should be forced, by circumstances or by another person, into selling their own body. No one should find themselves in such a hopeless place that they are at risk of violence and mental health trauma. As Christians, we want to see vulnerable women protected, not exploited.

We need to find a way, then, of deterring the number of men who pay for sex and protecting vulnerable women who find themselves in prostitution not out of choice, but because a lack of other options. At CARE, we want to see the purchase of sex criminalised so the burden of blame is shifted onto the buyer.

This approach is already used in Northern Ireland, where, under the Human Trafficking and Exploitation Act 2015, a new offence of purchasing sexual services was created. Since that law came into force, there have been a number of successful prosecutions. Around the globe, a growing number of countries are pursuing this progressive approach: Norway, Sweden, Iceland, Canada, Israel, France and the Republic of Ireland. It's time for Great Britain to do the same.

That's why at CARE we recently launched our not for sale campaign. We want to raise awareness about the absolute necessity of changing our current prostitution laws to make sure the buying of sex becomes illegal. The evidence tells us that such an approach helps to reduce demand for paid sex.

The not for sale campaign culminates in a member of the CARE team running the world-famous London Marathon on April 28. All the money raised will be used to help advocate for stronger laws that protect those in prostitution and offer them support to exit.

Today is a chance to send a message to policy makers across Great Britain: let's join the growing number of nations who have criminalised the purchase of sex. Let's send a message that buying sex from someone is not okay.

Nola Leach is chief executive of Christian Action Research and Education (CARE)