A long-awaited report on Russia’s activities in the UK has concluded that the Government “took its eye off the ball” and failed to respond to Moscow’s threat.

The heavily-redacted Intelligence and Security Committee’s report noted that there had been widespread allegations that Russia sought to influence voters in the 2016 Brexit referendum but it would be “difficult – if not impossible” to assess whether any such attempts had been successful.

But the committee said the Government was “slow to recognise the existence of the threat”.

It said the intelligence agencies and ministers should have been aware of the risk of Russian interference as a result of “credible open source commentary suggesting that Russia undertook influence campaigns in relation to the Scottish independence referendum” in 2014.

Publication of the committee’s report was postponed by Boris Johnson’s decision to call a general election and the subsequent delays in setting up the ISC in the new parliament.

The report and a press summary were prepared by the previous incarnation of the committee in the last parliament.

The committee said Russian influence in the UK is “the new normal” as successive governments have welcomed oligarchs with open arms.

There were Russians with “very close links” to Vladimir Putin who were “well integrated into the UK business, political and social scene – in ‘Londongrad’ in particular”.

The ISC said it was a priority to “mitigate the risk, and ensure that, where hostile activity is uncovered, the proper tools exist to tackle it at source and to challenge the impunity of Putin-linked elites”.

The ISC noted that “a number of members of the House of Lords have business interests linked to Russia, or work directly for major Russian companies” and these relationships should be “carefully scrutinised” given the potential for Moscow to exploit them.

It has been clear for some time that Russia under Putin has moved from potential partner to established threat, fundamentally unwilling to adhere to international law

The committee said: “It has been clear for some time that Russia under Putin has moved from potential partner to established threat, fundamentally unwilling to adhere to international law – the murder of Alexander Litvinenko in 2006 and the annexation of Crimea in 2014 were stark indicators of this.

“We therefore question whether the Government took its eye off the ball because of its focus on counter-terrorism: it was the opinion of the Committee that until recently the Government had badly under-estimated the response required to the Russian threat – and is still playing catch-up.”

The committee suggested that the prospect of interference in domestic political processes by the Russians was viewed as a “hot potato” which none of the intelligence agencies wanted to grasp.

“Open source studies have pointed to the preponderance of pro-Brexit or anti-EU stories on RT and Sputnik, and the use of ‘bots’ and ‘trolls’ as evidence of Russian attempts to influence the process,” the report said.

“We have sought to establish whether there is secret intelligence which supported or built on these studies.

“In response to our request for written evidence at the outset of the inquiry, MI5 initially provided just six lines of text.”

The committee called for the intelligence community to carry out a full assessment of potential Russian meddling in the 2016 referendum.

“Even if the conclusion of any such assessment were that there was minimal interference, this would nonetheless represent a helpful reassurance to the public that the UK’s democratic processes had remained relatively safe,” the committee said.

ISC member and SNP MP Stewart Hosie said: “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.”

Shadow foreign secretary Lisa Nandy said: “It is extraordinary that the Prime Minister, Boris Johnson, took the political decision last October ahead of the general election to block the publication of this important report that systematically goes through the threat Russia poses to the UK’s national security.

“The report is very clear that the Government has under-estimated the response required to Russia and it is imperative we learn the lessons from the mistakes that have been made.”

In a 20-page response to the report, the Government rejected the call for an assessment of alleged Russian activity during the Brexit referendum.

It said: “We have seen no evidence of successful interference in the EU Referendum.”

The Government also denied the suggestion it had “badly underestimated” the Russian threat.

“The Government has long recognised there is an enduring and significant threat posed by Russia to the UK and its allies, including conventional military capabilities, disinformation, illicit finance, influence operations, and cyber-attacks,” the official response to the report said.

“As such, Russia remains a top national security priority for the Government.”