Google suffered a setback Thursday after an advisor to the European Union's top court recommended it dismiss the tech giant's appeal against a record 4.1-billion-euro ($4.7 billion) antitrust fine.

Juliane Kokott, advocate general at the European Court of Justice, advised the court to throw out Google's appeal and confirm the fine, which was reduced in 2022 to 4.125 billion euros from 4.34 billion euros previously by the EU's General Court.

"In her Opinion delivered today, Advocate General Kokott proposes that the Court of Justice dismiss Google's appeal and, therefore, uphold the judgment of the General Court," the Luxembourg-based ECJ said in a press release Thursday.

The fine relates to a long-running antitrust case surrounding Google's Android operating system.

In 2018, the European Commission slapped Google with the record-breaking penalty on the grounds that it abused Android's mobile dominance to give unfair advantage to its own apps via pre-installation deals with smartphone makers. The Commission is the executive body of the EU.

Google said it was "disappointed" with the ECJ advocate general's verdict, adding it "would discourage investment in open platforms and harm Android users, partners and app developers."

"Android has created more choice for everyone and supports thousands of successful businesses in Europe and around the world," a spokesperson for the company told CNBC via email.

Though the advocate general's proposal is non-binding, judges tend to follow four out of five such non-binding opinions. The ECJ is expected to deliver a final ruling in the coming months.