Russian foreign minister Sergei Lavrov has said Moscow has ‘plenty of evidence’ that Britain staged the alleged chemical attack in the Syrian city of Douma.
Mr Lavrov even claimed that chemicals made in Salisbury were used by the UK.
In an interview with the state-run Rossiya Segodnya news agency, he also alleged that the humanitarian organisation the White Helmets falsified videos showing people suffering the after-effects of the gas attack in the Syrian city.
He accused the rescue organisation of terrorist links.
“Also, just recently, our defence ministry’s troops liberating Douma found a stockpile of chemicals produced in Germany, Porton Down and Salisbury, among others,’ Mr Lavrov said.
“Experts are now analysing the substances found there.”
The attack on 7 April was the trigger for US, UK and French air strikes in Syria.
Theresa May has said there is irrefutable evidence that the Assad regime was responsible for the deadly atrocity.
Assad and his ally Russia have both denied that this is the case.
The British ambassador to the UN warned earlier today that there is a “possibility” that Russia has tampered with evidence of the alleged chemical gas attack.
Karen Pierce said all the facts had not yet been established, and that Russia and Syria should allow inspectors to visit the site.
The visit to the area by inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) has been put on hold after a team came under small arms fire and returned to Damascus earlier this week.
Ms Pierce, speaking to the Associated Press, said: “We do look to the Russians and the Syrians to uphold the promises they made to the Security Council last week that the inspectors would be allowed in, that they would be escorted, that they would be safe and that they could have free access.”
Speaking last weekend, Prime Minister Theresa May said there was “no practicable alternative” than to use force to deter the use of chemical weapons by the Syrian regime.
She added: “This is not about intervening in a civil war. It is not about regime change.”