Travel website Trivago will likely face penalties in the eight-figure range.
The site has been found guilty of misleading consumers about cheap hotel deals.
A Federal Court judge in Australia has ruled Trivago's website and advertising didn't actually show customers the cheapest deals for hotel rooms.
Instead, it promoted advertisers who paid them the biggest fees.
The judge said Trivago did not provide an impartial, objective and transparent price comparison service...contrary to the impression it gave customers.
The company was also found guilty of false and misleading price comparisons, by comparing a standard room rate with a luxury room at the same hotel.
Australian disputes lawyer Shaun Temby told Mike Hosking that Trivago could face up to tens of millions of dollars in fines, as the issues have been going on for years and have affected millions of Australia.
"About 66% of the best prices put up on their website were not the best, and frequently the best prices were not put up."
Temby says that the headline claim that they would find you the best price is the main issue. The site is now expected to only say they are offering you some of the best prices.