A federal judge yesterday handed down a 286-page ruling in a case brought by the US Department of Justice and 11 state attorneys general four years ago.

Judge Amit Mehta said Google “is a monopolist, and it has acted as one to maintain its monopoly”, including by paying businesses like Apple to make Google the default search engine for its devices and browsers.

However, Google owner Alphabet has indicated that it will appeal the ruling, which could eventually end up before the Supreme Court.

US attorney general Merrick B. Garland said: “This victory against Google is an historic win for the American people. No company – no matter how large or influential – is above the law. The Justice Department will continue to vigorously enforce our antitrust laws.”

Assistant attorney general Jonathan Kanter, of the Justice Department’s antitrust division, added: “This landmark decision holds Google accountable. It paves the path for innovation for generations to come and protects access to information for all Americans.

“This victory is a reflection on the tireless efforts of the dedicated public servants at the Antitrust Division and our state law enforcement partners whose work made today’s decision possible.”

In a statement, Kent Walker, Google owner Alphabet’s president of global affairs, said: “This decision recognises that Google offers the best search engine, but concludes that we shouldn’t be allowed to make it easily available.

“We appreciate the court’s finding that Google is ‘the industry’s highest quality search engine, which has earned Google the trust of hundreds of millions of daily users’, that Google ‘has long been the best search engine, particularly on mobile devices’, ‘has continued to innovate in search’ and that ‘Apple and Mozilla occasionally assess Google’s search quality relative to its rivals and find Google’s to be superior’.

“Given this, and that people are increasingly looking for information in more and more ways, we plan to appeal. As this process continues, we will remain focused on making products that people find helpful and easy to use.”