According to the Open Society Foundation study, police practices made it more likely that sex workers would have unprotected sex with their clients.

The report "Criminalising Condoms" surveyed sex workers in Kenya, Namibia, Russia, the US, Zimbabwe and South Africa.

The director of the organisation's sexual health and rights project, Heather Doyle, said: "While one arm of government works to get condoms into people's hands, another is taking them away."

The report states that more than 40% of the prostitutes surveyed said the police had taken their condoms from them.

In Russia, this figure rose to 80% and, in some locations, sex workers reported that police destroyed condoms found on them.

In Namibia, 50% of sex workers surveyed said police destroyed their condoms and 75% of them had unprotected sex with clients as a result.

In the US, 52% said they sometimes chose not to carry condoms because of stop-and-search harassment.

The study found that police also use condom possession to justify arresting people on charges related to sex work.

The organisation, which advocates the decriminalisation of sex work, said the continued criminalisation of prostitution, and the use of condoms as evidence, made sex workers particularly vulnerable to police abuse.

In all six countries, the survey found that police physically and sexually abuse sex workers who carry condoms.

"Again and again, sex workers have told us that they are afraid to carry condoms because they worry it will mean being harassed or arrested by the police," said Doyle. "The police are punishing people for doing the right thing, for carrying condoms and trying to protect their health."

Police spokesman Captain Dennis Adriao yesterday disputed the findings of the study, saying the police had not received reports of police seizing condoms from sex workers.

"The fact that a person is in possession of condoms does not prove under South African law that the person is a sex worker.

"Furthermore, the SAPS, as part of the government, supports the Health Department's efforts to distribute free condoms," he said.