Britain has accused Russia of spreading "half-truths and half-lies" in a UN debate over a nerve toxin attack on a Russian double agent, while Russian officials quoted British opposition politicians to raise doubts about the allegations.
Britain accuses Moscow of using the Soviet-era military-grade nerve agent Novichok in an attack on former Sergei Skripal and his daughter, who are critically ill in hospital, a charge which Russia has denied.
Russian diplomats told the Conference on Disarmament at the United Nations in Geneva that Britain was not living up to its obligations by failing to share evidence with Moscow on the case and said Russia should be considered innocent until proven guilty.
"We would note that even the leader of the (British opposition) Labour party Jeremy Corbyn has asked to have at least a parliamentary appraisal of the investigation, but he has also received negative response, and I don't need to comment any further on this," Denis Davydov, a Russian representative, said on Tuesday.
Russia's destruction of its chemical weapons after the fall of the Soviet Union had been verified, and Russia had not conducted any research into Novichok although research continued in Britain and possibly in many other countries, he said.
The attack on the Skripals took place in the town of Salisbury, close to the British government's laboratory at Porton Down, which had the potential to produce Novichok, Davydov added.
One of the ingredients also existed in the United States for a long time, he said.
British ambassador Matthew Rowland said Russia was using "a series of wild hypotheses and half truth and half lies" to deflect attention from the truth, and its claim to have destroyed Novichok was "not clear at all".
Rowland disagreed with Davydov that Russia had a right to see the evidence, saying he was trying to confuse the picture with misleading procedural arguments.
"Russia's attempt to hide behind a false interpretation of the chemical weapons convention should fool no one," he said.
US disarmament ambassador Robert Wood said Russia's suggestion that the nerve agent used against Skripal could have come from a British or a US facility was "just absurd" and an example of typical Russian propaganda in which Moscow blamed others for what it itself had done.
Davydov said Moscow had been met with ultimatums when it answered Britain's questions, and British sources could not necessarily be trusted.
"We all remember very well that public opinion in that country believed the word of Prime Minister Tony Blair when he led his country into the Iraq war. He confirmed and was completely convinced that the Saddam Hussein regime possessed chemical weapons, but as it turned out he himself was set up by his own allies."