Questions are being asked about whether police are overstepping the mark in a crack-down on illegal foreign prostitutes.

Twenty-seven Asian sex workers have been deported as a result.

Prostitution is legal for New Zealanders but illegal for those here on temporary work visas, which is why Immigration New Zealand is beefing up its searches.

Immigration advisor Tuariki Delamere told Kate Hawkesby the Prostitution Law Reform Act requires police to have a search warrant.

"I've got videos of them breaking and entering, assaulting the owners, conducting illegal searches and that goes for Immigration New Zealand as well."

Delamere says the girls may be breaking the law but it's untenable police and Immigration New Zealand break the law to find two consenting adults having sex.

LISTEN ABOVE AS TUARIKI DELAMERE SPEAKS WITH KATE HAWKESBY