The existing rule in the area allows for up 12 guests before a resource consent needs to be applied for. But the consent is guaranteed and the rule is rarely enforced.
"If you want more than six you would have to get a resource consent and if there's a resource consent other provisions may apply and there's no guarantee you will get approved," said Leslie Preston, of Coromandel Peninsula's Bachcare, which manages holiday homes.
"That is really taking away holiday homeowners rights, it's a small group of commercial accommodation providers using the district plan process to restrict the rights of homeowners."
Ms Preston was concerned the move could result in holidaymakers going elsewhere, and was worried a lack of revenue could force some holiday homeowners to sell their properties.
Many Coromandel houses were unoccupied second homes that contributed a large amount of rates.
Motel Association chief executive Michael Baines said his organisation had been lobbying the Thames council - and other councils in holiday hotspots including Taupo, Ruapehu and Queenstown - about the issue.
He said apartments, bed and breakfasts and holiday homes fitted under the same permitted-use clause as motels, hotels and holiday parks but did not have to meet the same health and safety standards that commercial operators do.
Private accommodation providers also paid less for waste collection, wastewater charges and power, he said.
"So they can operate a hell of a lot cheaper so they are being subsidised by the ratepayer ... at the expense of the commercial provider who is working his butt off."
Mr Baines said private accommodation was undercutting moteliers during the high season from mid-December to the end of March.
Thames-Coromandel mayor Glenn Leach said he would meet Bachcare to discuss the matter.
Home renting rules
What's happening?
The New Zealand Motel Association is lobbying councils around the country saying private landlords should apply for resource consent because they do not have to meet the same health and safety standards they do. They say private landlords pay less for waste collection, wastewater charges and power, effectively undercutting moteliers.
What's going on in the Coromandel?
The Thames Coromandel District Council district plan review committee has approved a plan for its draft district plan that recommends that visitor accommodation for more than six paying guests a night will require resource consent.
What next?
The draft district plan will go before the council for sign-off at its last meeting before elections on October 2. The proposed district plan will be out for formal public consultation in November.