Google could be ordered to break up its operations after a US federal judge ruled that the company has an illegal monopoly over online search, according to a report.

The US Department of Justice is considering ordering Alphabet, Google’s owner, to divest parts of the search business, which could include the Android operating system and Google’s web browser Chrome, Bloomberg reported.

Alphabet’s shares fell 1.1 per cent to $164.18 in after-hours trading in New York after the article was published.

Last week Judge Amit P Mehta found that Google, which handles about 90 per cent of the world’s internet searches, exploited its market-leading position to exclude competitors.

Mehta noted that Google had paid $26.3 billion in 2021 alone to maintain its dominant market share and ensure that its search engine is the default on smartphones and browsers.

“Even if a new entrant were positioned from a quality standpoint to bid for the default when an agreement expires, such a firm could compete only if it were prepared to pay partners upwards of billions of dollars in revenue share,” Mehta wrote in his ruling.

He added: “Google, of course, recognises that losing defaults would dramatically impact its bottom line. For instance, Google has projected that losing the Safari default would result in a significant drop in queries and billions of dollars in lost revenues.”

The ruling against Google paved the way for a second trial to determine potential fixes.

Alternatives to a forced break-up could include forcing Google to share more data with competitors or actions to ensure it does not gain an unfair advantage in AI products, Bloomberg reported.

Google has said it plans to appeal against the ruling.

Apple, Amazon and Meta Platforms, the owner of Facebook, are also facing antitrust cases in the US.

A spokesman for the Justice Department said it was “evaluating the court’s decision and will assess the appropriate next steps consistent with the court’s direction and the applicable legal framework for antitrust remedies”.

He added: “No decisions have been made at this time.”

Google declined to comment.