Sex workers around the world face violence, rape, widespread discrimination and extortion, a global human rights watchdog said, with male or transgender sex workers facing further stigma from the police, clients and the community.
Research published by Amnesty International showed that sex workers globally lack protection from "horrific" abuse and violence -- even in countries like Norway, which are perceived to have strong human rights laws.
From Papua New Guinea to Argentina, Hong Kong and Norway, researchers consistently found cases of sex workers being physically and sexually abused by clients and the police.
"Sex workers are experiencing horrific levels of violence and abuse throughout the world," said Kate Schuetze, a policy adviser at Amnesty International.
In many cases police are the perpetrators of the abuse, making sex workers reluctant to report the crime, especially if prostitution is illegal in their country, Ms Schuetze said.
She added that sex workers caught carrying condoms -- seen by police as evidence of illegal activity -- have been arrested or targeted for extortion, which in turn discourages safer sex practices.
Mona, a sex worker in Papua New Guinea, said she was raped by several police officers after being caught with a client.
"I don't have any support to come to court and report them. It was so painful to me, but then I let it go," Mona was quoted by Amnesty as saying.
"If I go to the law, they cannot help me as sex work is against the law in PNG."
In April, France followed Northern Ireland, Canada, Sweden, Norway and Iceland in introducing legislation to make it an offence to buy sex.
Some activists said shifting the criminal charge from victim to the client would make countries like France less attractive for pimps and traffickers.
But male sex worker Luca Stevenson said conflating sex work with sex trafficking was problematic.
"Calling for an end to sex work to end trafficking for sexual exploitation doesn't make sense. It will and it does push sex work underground," said Mr Stevenson, a co-ordinator at the International Committee on the Rights of Sex Workers in Europe.
"The reality is the large majority of sex workers make a decision to sell sex," he told the Thomson Reuters Foundation.
Globally, almost 21 million people are trapped in forced labour, of which 4.5 million are victims of sexual exploitation, according to the International Labour Organisation.
"We're absolutely opposed to things like trafficking, the sexual exploitation of children," said Schuetze.
But, she said, overly broad anti-trafficking laws can also trample on the rights of people engaging in sex work consensually as adults.
Amnesty, which has called for the full decriminalisation of sex work, wants governments to create policies to protect adults who consent to selling sex for money.
For male or transgender sex workers in more conservative countries, such policies could result in less discrimination and better access to healthcare and other services.