Immigration New Zealand is stepping up border security and brothel checks to clamp down on overseas prostitutes arriving to work illegally during the Rugby World Cup.

"Extensive planning has taken place by all the border agencies to ensure that there are resources in place to allow the smooth movement of genuine travellers coming here for the Rugby World Cup," said Steve Stuart, general manager intelligence, risk and integrity.

"Major international sporting events are likely to increase demand for sex workers, and we are ready for that."

Yesterday, an Auckland brothel-keeper was convicted for attempting to smuggle a prostitute into the country.

Gordon Dong was found guilty of aiding and abetting the unlawful entry of a person into New Zealand, and sentenced to 300 hours of community work.

Dong had lied to an immigration officer last July saying the woman was here for a holiday, when she was going to work for him as a prostitute.

"This was an attempt at people smuggling which exploits the vulnerable for personal financial greed and we have zero tolerance towards such wilful abuse of the immigration system," Mr Stuart said.

"It serves as a warning to those who may be tempted to take advantage of the Rugby World Cup that we will not tolerate this activity or any immigration abuse."

Although prostitution has been decriminalised, it is illegal for anyone on a temporary visa, such as tourists or international students, to work in the sex industry.

Around 85,000 fans are expected to start arriving from August, and brothel owners are expecting a boom.

One brothel owner says he has already been contacted by sex workers from Asia and even some from Germany wanting to work here during the six week competition period.

"We don't smuggle them into the country ... these girls come on their own accord, willingly, and we just give them a place to do their work," he said.

Sex workers will be taken on as "tenants" rather than contractors or employees to ensure the brothel was not responsible for their immigration status, he said.

"Of course we'll be charging them a premium to rent a bed, like any other room rental establishment during the period, and it's really up to them if they want to pass on the cost to their clients."

National co-ordinator Catherine Healy says prostitutes working here illegally are predominantly Chinese, and will be enlisting the help of its Chinese-speaking staff member to advise brothel operators to stay legal.