This is part of a pro-Kremlin disinformation campaign on the poisoning of Russian opposition leader Alexei Navalny after the use of a chemical nerve agent of the Novichok group was established beyond any doubt by a specialist Bundeswehr laboratory.
In September 2017, the Organisation for the Prohibition of Chemical Weapons (OPCW) confirmed the full destruction of the 39,967 tons of chemical weapons possessed by Russia, but Novichoks were never declared to the OPCW and were not included in the Chemical Weapons Convention until 2019.
After the poisoning of Sergey and Yuliya Skripal with Novichok in Salisbury in 2018, Dr. Vil Mirzayanov said that “many countries could have had test samples, but production was only refined in the U.S.S.R. and Russia” and that Russia had to be behind the attempt on the Skripals because it “is the country that invented it, has the experience, turned it into a weapon... has fully mastered the cycle.”
Most of what we understand of Novichok agents comes from testimony and memoirs of Dr Vil S. Mirzayanov, the Chief of the Department of Counteraction against Foreign Technical Intelligence at the Russian State Union Scientific Research Institute for Organic Chemistry and Technology (GosNIIOKhT) who authored a 1994 report with the Stimson Centre describing the state of chemical weapon disarmament in Russia, revealing Novichok's existence. Mirzayanov said that only Russia would have the capability to deploy the agent.
Later on, in 1998, the US National Bureau of Standards, now the National Institute of Standards and Technology, added Novichok to its spectral data which has 300,000 compounds and is regularly updated.
A recently published year-long investigation by Bellingcat has discovered evidence that Russia continued its Novichok development programme long beyond the officially announced closure date.
There are also other cases following the same trend of disputing Navalny's poisoning and the use of Novichok by Russian state operatives, which can be found here and here.