RUSSIA has suggested that UK intelligence officers may have been involved in the poisoning of Sergei and Yulia Skripal in Salisbury and claimed that Britain has to prove it was not involved.

Britain insists there is no plausible alternative explanation for the March 4 Novichok attack, and has dismissed a series of suggestions emanating from Moscow as nonsense.

But the Russian Ministry for Foreign Affairs said that the onus was now on London to prove that its intelligence agencies were not involved.

In a statement, the MFA accused London of launching “a large-scale political and media campaign against Russia”, while refusing its requests to share samples of the toxic agent.

“We see a deliberate and purposeful escalation of confrontation and a demonstration of military force on Russia’s border. It is an obvious effort to undermine the political and diplomatic interaction that could lead to an objective and comprehensive investigation of the Salisbury incident.

“The analysis of all these circumstances shows that the UK authorities are not interested in identifying the real causes and the real perpetrators of the crime in Salisbury, which suggests a possible involvement of the UK intelligence services.

“Unless we receive convincing proof of the opposite, we will regard this incident as an attempt on the life of Russian citizens as part of a large-scale political provocation. We emphasise that the burden of proof rests solely on the UK.”

The Foreign Office declined to comment on the latest Russian statement, but previously tweeted: “Russia has responded to the Salisbury incident in the same way they have to every other case where they’ve flouted international law ... with denial, distraction and disinformation.”

The Kremlin allegation came as Moscow faced increasing global isolation, with at least 26 countries expelling a total of more than 130 suspected spies in response to Russia’s apparent use of a nerve agent in British streets.