Nick Kaldas​ told a parliamentary committee on the regulation of the industry that it should consider creating a register of sex premises, including a list of sex workers as well as owners and managers.

"These lists could then be cross-referenced with the NSW police force missing persons' lists, and would be invaluable for our federal colleagues when checking on visa issues," Mr Kaldas said.

Police estimated there were about 340 brothels operating in Sydney, said Mr Kaldas, who highlighted the difficulty in getting exact figures as "one of the problems we face".

"You cannot regulate establishments you simply don't know about," he said.

However, Mr Kaldas told the inquiry "there are clearly issues in the industry, in terms of servitude, the use of illegal workers and extortion by or involvement of organised crime and outlaw motorcycle gang groups".

He cited anecdotal evidence of Asian sex workers on student or tourist visas being kept as sex slaves, having their passports confiscated or being forced to take drugs with clients.

Police intelligence also connected outlaw motorcycle gangs to about 40 brothels, while several karaoke venues in south-western Sydney "were found or are suspected of providing sexual services and employing illegal Asian workers", he said.

"The [karaoke] venues identified also appear to have links to Asian organised crime networks," he said.

The deputy commissioner said the committee should consider background checks for brothel operators and banning those who had been banned in other jurisdictions.

Councils would be the "logical choice" to be the primary regulatory authority, said Mr Kaldas, who described the current situation as "ambiguous".

"We do not accept that regulating the industry properly will force it underground, as some may argue," he said.

"As it is right now, there is next to no regulation, no enforcement, and abuses are far more likely to go undetected, with horrible consequences for individuals."

But the idea of keeping a list of all sex workers was criticised by two public health experts, one of whom also questioned the frequency of sexual servitude cases in Sydney.

Professor Basil Donovan, the head of the sexual health program at the Kirby Institute, said police were "often being manipulated" by legal brothel owners making false allegations to try to shut competition.

"I see a lot of people who are more in servitude relationships than most, and they tend to be cooks and kitchen hands," Dr Donovan said.

"The sex workers, the women who were in debt bondage relationships, they literally dried up with decriminalisation."

Dr Donovan said no one would want to go on a register of sex workers and so "immediately everyone evaporates into the bushes".

"That system has been shown to fail for 150 years; no one has ever shown it to succeed," he said.

Phillip Read​, the acting director of the Kirketon Road Centre, also described the idea of a list as an "unmanageable disaster".

"We have trouble sometimes getting people to register for Medicare, let alone a brothel or a sex worker list," Dr Read said.

Mr Kaldas told Fairfax Media his comments were "simply suggestions from the operational police for the committee to consider".

"We're not wedded to anything. It's simply a discussion we think we need to have about making sure that we can identify when people are being abused," he said.