Two sources said the former trade secretary’s account was broken into multiple times between July and October last year, Reuters reported.
They declined to name which Russian group or organisation they believed was responsible, but said the attack bore the hallmarks of a state-backed operation, Reuters said.
The 451-page dossier was unveiled dramatically by Jeremy Corbyn before last December’s general election 2019, who said it left Boris Johnson’s claim that the health service was off limits “in tatters”.
US negotiators were pushing for “full market access” to the NHS and had “pushed hard” to extend patents on drugs developed by American corporations, potentially hiking UK prices.
The Conservatives accused Labour of peddling “conspiracy theories” – and, last month, Dominic Raab claimed “Russian actors” had sought to interfere in the election, with a criminal investigation underway.
Among the hacked information was six tranches of documents detailing British trade negotiations with the United States, Reuters reported.
They were disseminated online by a Russian disinformation campaign, something confirmed and condemned by the foreign secretary last month.
The news organisation said it was not able to determine which of Dr Fox’s email accounts was hacked and when it was first compromised.
It is not clear if the documents were stolen before he was sacked as the trade secretary on 24 July, when Mr Johnson entered Downing Street.
The subsequent leak of the classified documents, within weeks of the election, will be seen as one of the most blatant examples of suspected Russian attempts to meddle in British politics.
Last month, the powerful intelligence and security committee found that Moscow had tried to influence a referendum on Scottish independence in 2014.
It’s long-suppressed report also attacked the failure of successive governments to investigate suspected Russian attempts to deliver the 2016 Brexit referendum for Leave.