Russia sees the UK as one of its “top targets” in the West, according to the Intelligence and Security Committee.
The ISC’s long-awaited report said Russian influence in the UK was “the new normal“, and accused successive governments of welcoming the country’s oligarchs “with open arms”.
It called for “immediate action” to help intelligence services tackle “this very capable adversary”.
The committee also criticised No 10 for delaying the report’s publication.
Downing Street was accused of holding back its release ahead of December’s UK election – which it has denied.
But speaking at a press conference to launch the report, one of the ISC’s committee members, Kevan Jones, criticised the prime minister for not signing it off sooner, saying there was “no reason for delay”.
The ISC’s inquiry covers a number of topics, including disinformation campaigns, cyber tactics and Russian expatriates in the UK.
But much of the “highly sensitive” detail will not be published due to fears Russia could use the evidence to threaten the UK.
The report said the UK was “clearly a target” for disinformation campaigns around its elections, but the issue was described as a “hot potato” – with no one organisation taking a lead to tackle it.
ISC committee member Stewart Hosie said no-one in Government wanted to touch the issue of Russian interference with a “10-foot pole” and no-one knew if Russia had tried to interfere with the 2016 referendum “because they did not want to know”.
He told reporters: “There has been no assessment of Russian interference in the EU referendum and this goes back to nobody wanting to touch the issue with a 10-foot pole.
“This is in stark contrast to the US response to reported interference in the 2016 presidential election.
“There should have been an assessment of Russian interference in the EU referendum and there must now be one, and the public must be told the results of that assessment.”