"Russia is seeking to undermine the international system. That much is clear," Ciaran Martin, head of Britain's National Cyber Security Centre (NCSC) said at a London tech conference, according to his office.
"Russian interference, seen by the NCSC over the past year, has included attacks on the UK media, telecommunications and energy sectors," Martin said.
The centre has coordinated the government's response to 590 significant incidents since its launch in 2016, although the government agency has not detailed which were linked to Russia.
Prime Minister Theresa May on Monday accused Moscow of "seeking to weaponise information" and "sow discord in the West and undermine our institutions".
Russia's cyber activities include "deploying its state-run media organisations to plant fake stories and photo-shopped images", she said in a speech.
The scathing criticism was rejected by Russia's foreign ministry, which accused May of trying to distract the British public from problems at home.
Moscow's alleged attempts to influence last year's referendum on Britain's membership of the European Union are part of investigations under way in London.
May told lawmakers on Wednesday that parliament's intelligence and security committee would be looking into Russian interference.
Meanwhile parliament's digital, culture, media and sport committee has requested data from Twitter and Facebook on Russia-linked accounts and aims to interview social media executives at the British embassy in Washington early next year.
- Pro-Brexit 'bots' -
Damian Collins, the committee chairman, said it was "beyond doubt" that Russia has interfered in UK politics.
He said there was a pattern of behaviour of Russian organisations seeking out opportunities to create division, unrest and instability in the West.
"Foreign organisations have the ability to manipulate social media platforms to target voters abroad," he told AFP.
"This is seriously-organised buildings of hundreds of people engaged in propagating every day fake news through social media."
He said it was "terrifying" how cheap and easy it was for them to reach millions of people.
"It is one of the biggest threats our democracies face and we have to be serious about combatting it," Collins added.
May's spokesman insisted: "There has been no evidence of successful interference in our electoral processes."
Researchers at the University of Edinburgh, who examined 2,752 accounts suspended by Twitter in the United States, found 419 were operating from the Russian Internet Research Agency and attempting to influence British politics, The Guardian reported.
Professor Laura Cram, the university's neuropolitics research director, told the newspaper they tweeted about Brexit 3,468 times -- mostly after the June 23 referendum.
The content overall was "quite chaotic and it seems to be aimed at wider disruption. There's not an absolutely clear thrust. We pick up a lot on refugees and immigration", she said.
Meanwhile researchers at Swansea University in Wales and the University of California, Berkeley, have found more than 150,000 Russian-based Twitter accounts which may have influenced the Brexit referendum.
The social media accounts switched their attention to EU membership in the run-up to the referendum, 2016, according to research outlined in The Times newspaper.
Many of the accounts were fully-automated "bot" profiles which posted hundreds of tweets daily, or "cyborg" accounts which were partially run by people, the newspaper said.
The majority of the posts were pro-Brexit, while some supported remaining in the European Union.
Meanwhile it was revealed that a tweet which caused a furore after the Westminster terror attack in March originally came from a trolling agency account which, according to evidence before the US Congress, is backed by the Russian government.
The tweet showing a picture of a woman in a headscarf walking next to a victim, with the words: "Muslim woman pays no mind to the terror attack, casually walks by a dying man while checking phone".