Sweden set the trend in Europe by outlawing paying for sex in 1999. British Home Office officials have travelled to countries including Sweden to study the laws.
Across Europe, laws vary: In the Netherlands, famed for Amsterdam's "red light" district, prostitution is legal and street prostitution is confined to managed zones, although the city wants to partially reverse full legalisation introduced in 2000, because it has not achieved its aim of bringing the profession out of the shadows and protecting sex workers.
Denmark legalised prostitution in 1999; prostitution is legal in Germany on and off the street, but coercing prostitution is an offence. In France, like in Britain, prostitution is not illegal, but touting on a public highway and pimping are offences.
The trade thrives under a hotchpotch of restrictions that evolved over years: in Britain, brothels are illegal, but "saunas" and "massage parlours", many of which are fronts for prostitution according to police, operate with licences issued by local authorities.
British society has been tolerant of prostitution for so long it will take time to make men understand that the trade is harmful to women, Matthews said.
"The UK has a very long established tradition that paying for sex is OK, it's a man's right," he said. But he said new research shows many men who visit prostitutes are not highly motivated, and could be dissuaded by penalties or education.
"They said it was like buying a curry at the grocery shop. The motivation is actually a lot lower than many people assume. They would buy sex if it was there - if it's not there, they would go do something else," Matthews said.
"You could actually have this shift where people no longer think paying for sex is a legitimate activity."
CONSENT
The fact that so many trafficked women are forced into prostitution has injected the debate with fresh urgency.
The United Nations says a revolution in affordable transport and instant communication has increased trafficking over the past decade, with the trade now worth an estimated $30 billion.
Some 85 percent of women found working in British brothels are estimated to be from outside Britain, a reversal from 10 years ago when 85 percent of them were British citizens.
There are women who argue that they deserve the right to sell sex, and that prosecuting their customers would only make the trade more dangerous.
Amanda Brooks, a Texan former call girl and author of "The Internet Escort's Handbook", is among these who oppose any attempts to criminalise her trade.
"I understand why feminists want to reduce demand. I'm very sympathetic. I just think you need to be a little realistic. Even in the U.S. which has been heavily criminalising both buying and selling sex, it's still a thriving industry.
"There's always going to be the demand. The question is how do you regulate it so it's safest for everyone involved? I don't think the best way is to criminalise consenting adults."
There was no consent involved for Alicia. Free now after months of abuse, she is trying to come to terms with her experience.
"You always think: if I had been stronger, if I had talked out, if I had screamed to the outside world, maybe they would hear," she says.
"My thoughts were I wanted to just kill myself. But now I'm thinking it's worth it to be alive."
