Prime Minister Boris Johnson's government on Tuesday rejected claims it was suppressing a parliamentary report about possible Russian interference in British politics to avoid a scandal ahead of next month's snap election.

The probe by parliament's intelligence and security committee into suspected Russian covert actions in Britain's democratic process reportedly includes examining whether Moscow tried to interfere with the 2016 Brexit vote and the 2017 general election.

Moscow has been accused of spearheading sophisticated disinformation campaigns around the world to further its interests, including trying to manipulate elections in the United States.

The British committee, which oversees the work of the country's intelligence agencies, submits its reports to the government before publication to avoid the inadvertent release of sensitive information.

But a former head of domestic spy agency MI5 and the committee's chairman have suggested Johnson is stalling on the release of the 50-page report with the December 12 general election looming.

Jonathan Evans, head of MI5 from 2007 to 2013, told BBC radio: "If the government have a reason why this should not be published before the election, then I think they should make it very clear what that reason is."

Boris Johnson is accused of suppressing an intelligence report about possible Russian interference in British politics
Boris Johnson is accused of suppressing an intelligence report about possible Russian interference in British politics POOL / Tolga AKMEN

Dominic Grieve, an independent MP and the chairman of the committee, told lawmakers the intelligence agencies had already signed off on the report, which was then given to Downing Street on October 17.

He said it was "unprecedented" for its release to take so long and warned that if it was not published before parliament wraps up later on Tuesday ahead of the election, it might stay secret for months.

However Foreign Office minister Chris Pincher rejected "smears and conspiracy theories" in answer to a question on the issue in the House of Commons.

"It is entirely right that reports such as these go through an intensive security review before publication," he told MPs.

"It is not unusual for the review of ISC reports to take some time. The average turnaround time is six weeks."

Cambridge Analytica and GRU

Fears of Russian involvement in the election have been stoked following revelations that Moscow operatives directed a misinformation campaign on Facebook and other social platforms during the 2016 US presidential election.

Anti-Brexit activists demonstrate outside of the the Houses of Parliament
Anti-Brexit activists demonstrate outside of the the Houses of Parliament AFP / Tolga Akmen

Accusations have also persisted that Russia may have covertly intervened in the Brexit vote earlier that year.

A whistleblower from political consulting group Cambridge Analytica, which played a key role in the referendum, said last year it had used Russian researchers and shared data with companies linked to Russian intelligence.

It has also emerged that Russian officials in London held meetings with influential Brexit backers like Arron Banks, the single biggest donor to the anti-EU campaign.

Moscow has long denied allegations of hacking and meddling in foreign elections through social media disinformation campaigns, which are thought to be piloted by its GRU military intelligence agency.

The Russian embassy in London did not immediately respond to a request for comment on the British parliamentary report.

'Politically motivated'

Britain's government on Tuesday sought to play down concerns.

"There is no evidence to suggest there has been any successful Russian involvement in the British electoral cycle," Pincher said.

But the main opposition Labour Party said the report's delay was "clearly politically motivated".

"They realise this report will lead to other questions about the links between Russia and Brexit," said foreign affairs spokeswoman Emily Thornberry.

Beyond parliament, campaigning for the pre-Christmas election continued to gather momentum Tuesday, with Johnson and Labour leader Jeremy Corbyn trading blows over Brexit and Donald Trump.

The ruling Conservatives are trying to emphasise Labour's divisions over Brexit -- the defining issue in contemporary British politics -- while Corbyn is eager to highlight Trump's fondness for Johnson.

Labour, which is now pledging to hold another referendum on EU membership, is trailing the Conservatives by 11 percentage points in a poll of polls compiled by Britain Elects.

But the field also includes smaller pro-EU opposition parties that could potentially form a post-election bloc to stymie Brexit.