• A sign is seen at the entrance to the Google retail store in the Chelsea neighborhood of New York City, U.S.,

A sign is seen at the entrance to the Google retail store in the Chelsea neighborhood of New York City, U.S., (Photo : REUTERS/Shannon Stapleton)

Alphabet unit Google could face its biggest regulatory threat, with EU antitrust regulators set to open a formal investigation into its lucrative digital advertising business before the end of the year, said people familiar with the matter.

It would mark a new front by the EU competition enforcer against Google. It has in the last decade fined the company more than 8 billion euros ($9.8 billion) for blocking rivals in online shopping, Android smartphones and online advertising.

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An EU probe would focus on Google's position vis-a-vis advertisers, publishers, intermediaries and rivals, one of the people said, indicating deeper scrutiny than the French antitrust agency's case concluded last week.

Google made $147 billion in revenue from online ads last year, more than any other company in the world. Ads on its properties, including search, YouTube and Gmail, accounted for the bulk of sales and profits.

About 16% of revenue came from its display or network business, in which other media companies use Google technology to sell ads on their website and apps.

Both units are under fire. The U.S. Justice Department, joined by some states, sued Google last year for abusing its dominance in search ads. A group of states led by Texas in a later lawsuit focused on anti-competitive behaviour on the network side of the house.

France last week settled with Google for $268 million and various commitments over similar allegations related to the network business, and the unit also must work closely with Britain's competition regulator on upcoming software changes as part of a settlement reached days later.

The Commission declined to comment. Google did not immediately respond to a request for comment.