More police were having free sex services during undercover investigations, a sex workers' rights group said at a Wan Chai demonstration against abusive practices.
Zi Teng said the number of complaints it had received about officers getting free services before arresting a prostitute had more than quadrupled this year from last year.
Complaints about sex workers having their reports to police rejected or being denied phone calls after arrest were also rising, Zi Teng executive officer Ng Nga-shan said at the demonstration to mark the International Day to End Violence Against Sex Workers.
Police said complaints about such abuses could be made to the Complaints Against Police Office.
But Ng said it was unrealistic to ask violated sex workers to report their complaints to the police.
'Many are foreign or mainland workers. They are unfamiliar with Hong Kong's legal system and they do not even know that they have rights to complain about the abusive actions of police,' she said.