An agent in Sutton, Surrey, is protesting over huge hikes in his rates to FindaProperty. Dozens of other agents are affected.
He has been told that his subscription to The Digital Property Group will triple between next month and March.
The agent, who has asked not to be named, says it means the cost of advertising on Digital's sites, which include FindaProperty and Primelocation, will double - and will cost him considerably more than Rightmove.
The agent says he received two aggressive phone calls from sales staff at TDPG, which is owned by the Daily Mail, informing him that his subscription would go up in three staggered hikes.
He says the sales staff told him that the price increases would affect almost 800 agents within the M25 - although Digital told EAT the real number is in fact closer to 70.
He added: "I think they are very arrogant in their approach when the market is still depressed, and when you ask any agency about their revenue levels, they are still way down on what they were at the peak."
He also said he was unhappy with the makeover of the FindaProperty site back in May and the fact it now takes on third party advertising.
"In my opinion, the site looks awful. Advertising from third parties is all over the pages my properties are displayed on, as opposed to Rightmove which has none. In my opinion, this has degraded the website and TDPG are being very greedy. They have compromised the website."
He said his firm is receiving many less inquiries than a year ago, and believes he should get a price decrease. "There are many agents like me who will not put up with ridiculous increases," he added, saying that he had never wanted to be on Primelocation in the first place and that it was "a complete waste of time". TDPG puts it pricing for all its websites in one package, even where agents have no interest in listing on, for example, FindaProperty, or Primelocation.
It is believed that the agent in question, along with others in price negotiations, is currently on an old rate, below rate card.
In an official statement, Digital said: "The Digital Property Group rate card was created to provide a fair and transparent reflection of the value we deliver; it takes into account the agent's location, our market share as well as the number of properties listed and their average cost. By advertising on each of The Digital Property Group portals, agents benefit from inquiries across all levels of home buyer and renter as well as profit from the positive brand association with our portals - especially important when attracting new instructions.
"Our subscribers gain from significant investment into our portals through TV, radio, print, online and outdoor advertising across the country, not to mention the positive addition of Globrix.com into our portfolio. They also benefit from innovations such as our iPad app and the FindaProperty.com redesign which has yielded a significant number of enquiries and a record 3.8 million unique visitors in July.
"We cannot comment on specific cases but we would be very happy to speak to this customer on an individual basis and discuss our value to their business."