Rightmove is set to face legal action over accusations that it charges unfair and excessive fees to thousands of UK estate agents.
A group making a claim against the property website estimated that damages could total around £1 billion.
The case, which is being led by former panel member for the UK’s competition watchdog Jeremy Newman, is due to be brought to the Competition Appeal Tribunal.
Mr Newman said the claim will “seek to return the overpaid fees to estate agents across the country”.
He accused the firm of actions that “exploits its dominance of the online property portal market in the UK to charge excessively and unfairly high subscription fees, both at face value and when compared with its competitors”.
“Estate agents have had to absorb consistent, excessive price increases on a regular basis,” he added.
Thousands of estate agents will be represented in the legal action unless they choose to opt out.
In a statement to investors, Rightmove said it had “received notice of a potential claim”, adding: “We’re confident in the value we provide to our partners.”
Based on the estimated total damages and size of the class action, it is understood that the claim assumes agents can be charged thousands of pounds in fees to use Rightmove.
Rightmove has previously come under scrutiny with a petition gaining more than 2,000 signatures earlier this year calling for an investigation into its pricing model.
The firm has been accused of squeezing small businesses and independent agencies with fees that are higher than what corporate chains pay.
Mr Newman was formerly a panel member on the Competition and Markets Authority (CMA), which investigates markets, companies, and business deals if there are concerns that their might be unfair or anti-competitive behaviour.
The case is being funded by specialist litigation funder Innsworth Capital Limited.
Rightmove says it has the UK’s largest selection of properties for sale and to rent, with around 80% of all time spent on property portals being on its site.
The FTSE 100-listed firm made a pre-tax profit of £146.5 million over the six months to the end of June.
Subscribe or register today to discover more from DonegalLive.ie
Buy the e-paper of the Donegal Democrat, Donegal People's Press, Donegal Post and Inish Times here for instant access to Donegal's premier news titles.
Keep up with the latest news from Donegal with our daily newsletter featuring the most important stories of the day delivered to your inbox every evening at 5pm.