Scott Boutwell for BBC News
A landmark case will be heard in the Court of Appeal in London on Thursday, after a lower court ruled the government’s sex work laws were too vague.
Currently, it is illegal for prostitutes to advertise their services, or accept payment in any form.
Most British MPs oppose such legislation and want the laws to be repealed.
But the British government argues those who indulge in sex work are seeking to “trample on others’ rights”.
The three judges will hear a joint appeal from the government and the industry body Prostitutes’ International Network (Pins), which represents street-based prostitutes.
Lawyers for Pins say that the Acts are “unjust, unreasonable and unenforceable”.
They have asked the court to strike down two pieces of legislation – the 2003 Modern Slavery Act and the 2011 Sex Work (Prohibition) Act.
One of those acts was passed while former Prime Minister Gordon Brown was in office.
‘Unfair to individual women’
It bans “carrying, buying or obtaining services of a prostitute”, without permission.
Similar legislation has been criminalised in several countries, but the UK government argues the changes to sex work laws have been necessary to protect sex workers.
Analysis by Rob Carrick, BBC News, Glasgow
This is an immense case that may well change the way the sex industry operates in this country.
After Thursday’s hearing, the court could rule that the UK sex industry needs a whole new regulatory framework. Or the court may uphold the original judgement, with the Government insisting that it is “proper and proportionate” to reform the law and protect sex workers from harm.
A ruling for the Government would represent a devastating blow to the last remaining sector of women working in sex work in this country.
“I hope that this will give the necessary power to put pressure on the government to change its laws,” said Kim Howells, one of the MPs who first introduced the same legislation as Mr Brown’s Prime Minister.
However, many argue that the move is “discriminatory and unfair to individual women”.
Figures from the early stages of the campaign suggest the number of sex workers in Britain is close to 25,000, representing a 20% drop in the last 10 years.
This court battle has captured the imagination of sex workers and their families and could influence the way prostitution is regulated in the future in the UK.