Rightmove has been accused of trying to shut down its competition by removing a free online estate agent from its property listings.
Owner Sellers, an estate agent which charges no commission, has been de-listed from Rightmove for allegedly breaching its terms and conditions, but has said the allegations are false.
Rightmove has accused Owner Sellers of putting vendor contact details on sales boards outside houses, and of putting Rightmove's logo on its boards. But Owner Sellers say they have sent images proving this is not the case.
It's the fifth time Rightmove has taken steps against Owner Sellers in the last year.
"We can only assume that Rightmove sees us as an existential threat to their business model and to that of many high street agents, and they are doing their level best to stop us from delivering a service that vendors want," said Rupert Cattell, founder of Owner Sellers, said.
"This is the future of estate agency and clearly Rightmove doesn't like it."
The fifth audit of Owner Sellers by Rightmove is "a gross abuse of their position", Cattell said.
Rightmove and the traditional estate agents represent "Rip-Off Britain", according to Cattell, because they make vendors pay a commission for selling their home.
Owner Sellers charges for creating flooplans and for doing professional photography, but the vendors are in charge of organising viewings and marketing the property, meaning they can advertise on more than one property portal such as Rightmove and Zoopla.
On the vetting process, a Rightmove spokesperson said: "Rightmove's terms and conditions and membership criteria are designed to protect users, for example by ensuring that all property details appearing on Rightmove are reliable and that agent members have actually visited those properties, and also to ensure that all members comply with relevant UK legislation.
"We conduct a diligent but fair vetting process in respect of all applicants and we would refuse membership to any business that failed to meet those criteria."