No one has been prosecuted in New Zealand for human trafficking but critics say that is only because a difference in definition is allowing cases to slip under the radar.
A recent example is the case of a Malaysian sex worker who needed police help to retrieve her passport from her brothel owner.
Immigration New Zealand has ruled this does not constitute trafficking.
Agency head Nigel Bickle said his officials had visited the central Auckland brothel and spoken to its manager and sex workers, and are "satisfied there were no indications of exploitation".
The Malaysian sex worker, who was in New Zealand on a visitor's permit but has since returned home, told another prostitute there she had been paid $5600 to come to Auckland, and had been made to work 16-hour shifts with few breaks on most days.
Another Malaysian sex worker said she had been lured here with a $4500 cash offer, plus airfares, but was later told that it was a loan she had to repay.
Her passport was also taken from her soon after she arrived.
The Department of Labour, which oversees immigration, says New Zealand does not have any known history of people-trafficking and Mr Bickle said the agency had not seen any substantiated claims.
No trafficking offenders have been prosecuted here, but anti-trafficking advocates said the country's clean slate could be attributed to how New Zealand defines people-trafficking.
Unlike the United States definition, which includes domestic cases as trafficking, New Zealand recognises only international border crossing cases.
The annual US State Department's Trafficking in Persons report, which was released in June, said it was possible trafficking victims were not being detected.
"No research has been conducted to determine the full extent of the trafficking problem in New Zealand," the report said.
"It is possible ... that citizens and foreigners in New Zealand exploited in forced labour and the legal or illegal commercial sex trade have not been identified by the government as trafficking victims."
The US report said New Zealand was a source country for underage girls subjected to forced prostitution and a destination country for forced labour.
As well, it did not have a comprehensive anti-trafficking law.
Judy Boyle, who runs a trafficking awareness campaign called The No Project, said differences in definition often result in trafficking cases slipping under the radar.
"Even if she was aware that she was working as a prostitute, the fact that she didn't have her passport and she had to hand over her money make it seem like a classic trafficking in persons case.
"Every other thing pointed to trafficking," said Ms Boyle of the Auckland case.
Ms Boyle, who lives in Greece but is back in New Zealand to run a series of trafficking awareness workshops, believes increasing public awareness was the way to reduce trafficking.
The Government last year began a comprehensive plan of action to prevent people-trafficking led by the Department of Labour, which detailed actions needed to be undertaken by agencies including Customs, Police and the Ministry of Foreign Affairs.
The Labour Department is also undertaking research into international best practice in supporting and protecting trafficking victims.
Mr Bickle said: "Work is progressing according to the timetable, and we are prepared for a case of trafficking should one arise in the future."
What's been done since Government's action plan started last year?
*Multi-agency staff training on trafficking indicators and victim interviewing techniques.
*Multilingual awareness and outreach materials for victims produced.
*Training for all police investigative staff during induction.
*Victims of people trafficking to receive financial assistance while in NZ.
Victims of Trafficking immigration policy has been developed.
(Source: Immigration New Zealand)By Lincoln Tan Email Lincoln