The French competition authority has imposed a €150 million (£123m) fine on Google for anti-competitive behaviour and having unclear advertising.
The tech giant was accused of mistreating advertisers who bought its keyword ads, tactics that have been labelled "brutal and unjustified" by the French regulator.
The decision published today concludes a lengthy investigation into the company that found a policy of using "opaque and difficult to understand" rules on its Google Ads platform, and that these were then enforced in an "unfair and random manner".
The platform is used to display adverts to users as they browse Google's search engine, which appear as organic results. However, the investigation found that rules governing how these ads can be surfaced were unfair and inconsistent.
Google has said it will appeal the fine, however, it signals yet further scrutiny of how the company promotes content via search and advertising.
More specifically it relates to the rules Google applies to its Ads platform which set conditions under which advertisers can broadcast ads — rules the watchdog found to be confusing and inconsistently applied.
It also found Google had changed its position on the interpretation of the rules over time, which it said generated instability for some advertisers who were kept in a situation of legal and economic insecurity.
A lot of that pressure has come from France. In September, Google agreed to pay French authorities almost €1bn to settle a four-year fiscal fraud investigation.
For this latest fine, the chairman of France's competition authority, Isabelle de Silva, said Google had "the power of life or death for certain companies that live by these advertisements".
"We don't contest Google's right to impose rules," she said according to Reuters. "But the rules must be clear and imposed equally to all advertisers."
Last year Google accounted for more than 90% of all revenues earned from search advertising, according to the UK's Competition and Markets Authority, which also recently expressed concerns about companies like Google that had become "entrenched with negative consequences" for those that use it.
Google has said it will appeal the fine, but also confirmed it had suspended an advertiser that was "running ads for websites that deceived people into paying for services on unclear billing terms".
"People expect to be protected from exploitative and abusive ads and this is what our advertising policies are form," a Google spokesperson said. "We do not want these kinds of ads on our systems, so we suspended [the company] and gave up advertising revenue to protect consumers from harm."
