A federal judge has ruled that Google will not have to divest crucial parts of its digital advertising arm, rejecting the US Department of Justice's argument that a forced sale is the only way to dismantle its monopoly over the business. On Wednesday, Judge Leonie Brinkema denied the DoJ's request that Google be forced to sell its 'Ad X' advertising exchange and publisher ad server businesses.

The decision is the second time that a court has dismissed the DoJ's attempts to break up Google's parent company Alphabet, despite prosecutors winning the two cases by convincing courts the tech group held an illegal monopoly. Brinkema opted to enforce 'behavioural remedies' on Google, which will be determined later.

Both judges flagged the practical difficulties of forcing spin-offs of such large businesses and worried that technology would have moved on during years of appeals from Google, especially as AI shakes up the sector. Alphabet stock has risen 57 per cent over the past 12 months, helped by investors' relief that the company has survived a trio of antitrust losses with its core businesses intact.

However, the ruling was criticised by anti-monopoly campaigners as 'toothless' and with little chance of disrupting Alphabet's power. 'Judges keep finding Google guilty but it keeps walking away with both its ill-gotten gains and its empire intact,' said Laurel Kilgour of the American Economic Liberties Project.