The French competition watchdog said it considers that the Google Ads operating rules imposed by Google on advertisers are established and applied under non-objective, non-transparent and discriminatory conditions.
"The opacity and lack of objectivity of these rules make it very difficult for advertisers to apply them, while Google has all the discretion to modify its interpretation of the rules in a way that is difficult to predict, and decide accordingly whether the sites comply with them or not," the ruling said.
"This allows Google to apply them in a discriminatory or inconsistent manner. This leads to damage both for advertisers and for search engine users," it added.
In March, European Union's antitrust regulators fined Google 1.49 billion euros ($1.7 billion) for abusing its dominance in the online search market by blocking rivals.
Google has abused its market dominance by imposing a number of restrictive clauses in contracts with third-party websites which prevented Google's rivals from placing their search adverts on these websites, the European Commission (EC) said in a statement.
In a decision announced on Friday, the French competition authority ordered Google to clarify how it draws up rules for the operation of Google Ads and its procedures for suspending accounts.
A Google spokesman told TechCrunch that the company will appeal the decision.
Brussels last year hit Google with a record 4.3 billion euroes fine for abusing the dominant market position of its Android operating system for mobile phones.
( With inputs from IANS )