Google’s parent company Alphabet illegally dominated two online advertising technology markets, a US judge has found, writes Richard Marsden.

The case was the first of two brought by the American government in the space of a fortnight which may lead to the technology giant, worth €1.65trillion, having to sell off lucrative arms of its business.

In yesterday’s ruling, which applies to Google’s operations worldwide, District Judge Leonie Brinkema, sitting in Alexandria, Virginia, ruled that Google unlawfully monopolised separate markets for publisher advertising servers and ad exchanges – online structures which sit between buyers and sellers.

Next week, a judge will hold a trial in Washington after a request by the US Department of Justice to make Google sell its market-leading Chrome browser and take other measures to end its dominance in online searches.

Judge Brinkema found that Google was “wilfully acquiring and maintaining monopoly power” in violation of US antitrust laws over web advertising.

She added that Google illegally tied together its products to maintain its monopoly.

She also criticised “Google’s systemic disregard of the evidentiary rules regarding spoliation of evidence and its misuse of the attorney-client privilege”.

The ruling could allow prosecutors to argue for a break-up of Google’s advertising products.

The US Department of Justice has said that Google should have to sell off at least its Google Ad Manager, which includes the company’s publisher ad server and its ad exchange.

Google has previously explored selling off its ad exchange to appease European antitrust regulators, Reuters reported in September.

Judge Brinkema oversaw a three-week trial last year where prosecutors said Google used “classic” monopoly-building tactics of eliminating competitors through acquisitions, locking customers in to using its products, and controlling how transactions occurred in the online ad market.

Google argued the case focused on the past, when the company was still working on making its tools able to connect to competitors’ products.

The company also claimed prosecutors ignored competition from technology companies including Amazon.com and Comcast as digital ad spending shifted to apps and streaming video.

Next week’s hearing in Washington will be heard by District Judge Amit Mehta, who in an earlier hearing last August found the search giant had illegally monopolised the online search and advertising markets.

The US government have called for Google to be banned from signing multibillion-dollar deals with smartphone makers such as Apple to make Google Search the default search engine on devices, including the iPhone.

They also want to force Google to share data it collects from its search engine with its rivals in an effort to boost competition.

The US Department of Justice said: “The playing field is not level.”

Google was accused by Republicans last year of ‘censoring conservative speech’ prior to the presidential election.