In a lawsuit filed to the Federal Court in May, Domain alleged REA, which operates realestate.com.au, wrongly spruiked that it found buyers for nine in every 10 properties listed on its platform.
Domain claims the statements are not supported by the underlying data and has accused its competitor of breaching consumer laws.
A REA spokesperson said the company "stands by" the claims, saying they were based on analysis of one million sales and the findings had been independently verified by consultancy firm Deloitte.
REA has launched its own cross-claim over statements made by Domain which it alleges are false.
Domain's assertions that listings with its 3D modelling Matterport Suite receive 5.5 times more listing views and 4.2 times more buyer inquiries than comparable listings are misleading, REA alleges.
"These claims are based on a tiny sample of listings that were given disproportionate national exposure across the Domain homepage earlier this year," the REA spokesperson said.
The companies are Australia's largest providers of online residential real estate advertising, with each valued in the billions of dollars.
Domain's claims stem from publications including an April media release from REA which stated "realestate.com.au attracts the buyer for 9 in 10 listed homes that sell on the platform".
The release went on to state that the figures reinforce the platform as number one in the country in terms of the scale and quality of its audience.
REA repeated the claims in a statement to shareholders on the ASX, where it has a market capitalisation of more than $18 billion, as well as in a LinkedIn post.
The claims were also published by several news outlets including The Australian and promoted on a billboard outside the Gold Coast Airport.
The billboard stated: "We help 9 in 10 buyers find the one".
Domain claims the billboard was intended to be viewed by thousands of real estate agents who were arriving at the Gold Coast for a national conference.
REA has attributed the claims to its Buyer Impact Model, which analyses the browsing and viewing habits of the website's users.
Domain claims under the model, REA does not have the available data to conclusively say how many buyers actually viewed properties on its platform prior to purchasing a property and couldn't rule out that they had seen the property elsewhere first.
If Domain is successful in its suit, it is seeking that REA be prevented from advertising the claims further, in addition to any measures that the court sees fit.
Domain declined to comment.
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