Abacus Motel managers Robbie McCarthy and Jodie Mihajlovic said they received a letter several months ago from an anti-discriminatory group informing them it was against the law to deny a room to a sex worker.

"Apparently some motels in the Isa were denying rooms to working girls and an email was sent out to all hotels and motels," Mr McCarthy said.

"The sex workers who stay at our motel are always honest about what they do," he said.

"They are polite and clean, they clean their own rooms and always pay in advance.

"We never have any problems."

"We have more problems from random clients off the street."

Robyn Horn from the Oasis Motel said it was impossible to know if someone was a sex worker.

"You can't exactly ask someone up-front; it would be very insulting," Ms Horn said.

"The working girls are very quiet, you wouldn't even know they are here."

"They know it is against the law for them to proposition in-house guests and it never happens," she said.

Queensland State director of The Australian Christian Lobby Wendy Francis said it supported the Attorney-General's decision to investigate a ruling made against a Queensland motel that it breached the Anti-Discrimination Act by denying a sex worker a room," Ms Francis said.

"The issue raises the rights of businesses and motels across the state to decide what occurs on their premises."

But Mr McCarthy said he had never experienced any problems with sex workers in his establishment, but motel management should have the right to decide who stays in their motel.

"We can knock anyone back for whatever reason, except the sex workers."

"We have never had any problems, but down the track if something happened, it would be good to know we could refuse them.

"They really don't bother anyone else in the motel. We don't tell other guests who is working, for the sake of everyone's privacy."