Auckland Council says at least seven brothels known to be operating in an upmarket suburb are legally allowed to be there.
Of the seven brothels operating in Epsom, four are signed massage clinics along Manukau Road, while the other three are unmarked.
The council says it has received several complaints about the brothels over the past two years.
Three of the four signed brothels were fined and warned by the council for operating as a business in a residential zone.
However, after downsizing to fewer than four sex workers, the brothels are allowed to remain in the area and operate without a licence under the Prostitution Reform Act .
The council says all of the brothels will be further investigated to check they are operating within the law.
