Candice, a petite Chinese girl, fusses over a customer as she pours him a cup of oolong tea wearing nothing more than a see-through blood-red coloured camisole and knee-high fake leather boots.

But behind her smile and calm appearance, the 21-year-old sex worker on Auckland's North Shore confesses to be living on the edge.

"I have to look happy, but I worry all the time if there is an immigration check or even if my client is an undercover immigration officer," she said.

Candice is one of the many illegal prostitutes who arrive in New Zealand either on a visitor or student visa to work in the sex industry.

The arrival of illegal Chinese sex workers have driven an industry that has been decriminalised back underground, says the New Zealand Prostitutes Collective.

"We're now looking at two industries - an industry which is supported by decriminalisation, and an industry which is having to be underground again," said Catherine Healey, the collective's national co-ordinator, when asked how Chinese sex workers have influenced the sex industry here.

"Predominantly, the illegal part of the industry is Chinese," she said.

Although prostitution was decriminalised in 2003, it is illegal for those on a temporary visa, such as students and tourists, to work in the sex industry.

The collective does not record if a prostitute is working illegally, but Miss Healey said Chinese now make up nearly a third of the 1700 sex workers in Auckland - outnumbering Maori and Pacific Islanders, and behind only Pakeha.

Last year Immigration New Zealand, which only investigates when a complaint is received, found at least eight foreign sex workers working illegally.

A client, who frequents a Chinese "massage centre" in Takapuna, says the $40-per-hour charge was the draw.

"Even with everything included, it rarely goes beyond $80 with one of these Chinese girls," he said.

NZPC Auckland Manager Annah Pickering said other sex workers charged upwards of $100 per hour, and her organisation has produced a Chinese leaflet urging sex workers to "value themselves" and charge higher rates.

Miss Pickering said because of the large number of Chinese sex workers here, it was now an "integral part" of its operations to have many of its information and education brochures translated into Chinese.

A Chinese-speaking staff member had been employed by the collective, but she died suddenly from an illness earlier this year, and a replacement was being sought.

Miss Pickering said about a third of the brothels and massage parlours in Auckland are run by Chinese operators.

One of them told the Herald it was common to let sex workers "freelance" at his brothel in the CBD.

"They are just like customers renting a room from us. We do not employ them or pay them a commission, their customers are their paymasters," explained one central city operator.

"We don't know and we don't ask about their personal details, including their immigration status."

Chinese sex workers, who spoke to the Herald on the basis of anonymity, said money was the main reason they came here and none had plans to settle here.

"Even when I charge $80, it is more than I ever earn back in China," said a 21-year-old from Hunan, here on a student visa.

Despite her illegal immigration status, she felt "safe" working here because the only offence she was committing is with immigration and not the police.

A 19-year-old said she found New Zealand "boring" and believed she could do more with the money she earned here back in China.