MPs have threatened to sue Boris Johnson for failing to protect UK democracy from Russia.

The cross-party group have written to the Prime Minister warning he could be facing a court battle following publication of the Russia report earlier this year.

The report by the Intelligence and Security Committee found that the UK Government failed to look for evidence or signs of Russian interference in the Brexit referendum, despite examples of previous meddling in UK elections and votes in other countries.

Labour, Lib Dem, SNP, Green and ex-Conservative MPs and Lords have joined forces to tackle  Boris Johnson over his alleged lack of action on Russia.

The letter sent to Downing Street this week says Boris Johnson’s failure to hold such an investigation is a breach of the right to free and fair elections protected by Article 3, Protocol One (A3P1). 

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Caroline Lucas, Green MP for Brighton, who is a member of the group, said: “Democratic processes are clearly at risk and it seems that the integrity of our elections is being deliberately undermined.  Nothing could be more serious for our democracy.”

The group claims that the prime minister is deliberately trying to make the issue of Russian interference about Brexit when it’s actually about ensuring the integrity of future elections. It said it was bringing the case because of the ISC’s warning that without an effective investigation, there was ‘an unacceptable risk of repetition’. 

The legal action, they say, is a ‘last resort’ given Johnson’s refusal to acknowledge the national security implications of his failure to act. 

He now has two weeks to respond to the pre-action letter.

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The group includes Labour  MPs Chris Bryant and Ben Bradshaw, the Green MP Caroline Lucas, Alyn Smith for the  SNP, Lord Strasburger who sits on the Lib Dem benches in the Lords and Baroness  Wheatcroft, a Conservative peer until she resigned from the party last year. 

The Citizens, a new non-profit group whose mission is to hold power to account, launched a Gofundme to pay for the legal action and have asked people to help to defend Britain’s democracy not just against interference from abroad but from its own government.    

Tessa Gregory, a human rights lawyer with Leigh Day who is representing the group, said that under the Convention, countries had to not only ensure that free and democratic elections take place but that they do so under ‘conditions which will ensure the free expression of the opinion of the people in the choice of the legislature’.    

She said that A3P1 also obliges governments to investigate arguable violations of Convention rights where there is credible evidence of foreign state interference in a democratic electoral process.   

The Citizens say that they had no choice but to look at legal options given the government’s refusal to take on board the ISC’s findings or even to answer questions on the matter. Baroness Wheatcroft said that the government was showing ‘contempt’ for the democratic process in ‘failing to do it all it can to protect its integrity’.    

It puts pressure on the prime minister in a week in which the Senate Intelligence  committee in the US published details of Russian citizens with strong links to UK politics,  including Oleg Deripaska who was named as a ‘proxy’ of the Kremlin and who has holidayed with both the ex-Chancellor, George Osborne, and Lord Mandelson.  

Alyn Smith, SNP MP for Stirling, who is also involved in the ction, said: "Having take the UK government all the way to the European Court of Justice in the Article 50 case I’m proud to join another cross party action on another important subject. "It staggers [me] that anyone can say with a straight face there’s no evidence for something when the real issue is they haven’t looked.

"The fact we are having to take  legal action is proof that under this government all other checks and balances are simply not functioning.”

A Cabinet Office spokeswoman said: "Safeguarding our democracy will always be an absolute priority and the UK has robust systems in place to protect our elections from interference.

“To prevent against any future threats we are bringing forward new legislation to provide the security services and law enforcement agencies with the tools they need to disrupt hostile state activity

"And we have also published proposals for a digital imprint regime that will improve transparency in political campaigning online, and are developing an online media literacy strategy, to help empower the public to question the information they read online."