Russia has warned Britain that it was "playing with fire" by blaming it for poisoning former spy Sergei Skripal and his daughter Yulia last month.
At a UN Security Council meeting on Thursday night there were smiles and a handshake between the Russian and British ambassadors, but no sign of reduced tensions.
"We have told our British colleagues that 'you're playing with fire and you'll be sorry'," Russian ambassador Vassily Nebenzia said.
"Novichok is not copyrighted by Russia in spite of the obviously Russian name.
"It is a name invented in the West for a line of toxic substances, which are nothing new for experts and scientists, and developed in many countries including the US and Britain."
But Britain defended its actions in the aftermath of the incident in the town of Salisbury, which has included expelling Russian diplomats from the UK and encouraging more than a dozen Western countries to do the same.
British ambassador Karen Pierce said: "We cannot ignore what has happened in Salisbury. We cannot ignore Russia turning a blind eye to the use of chemical weapons in Syria and in Salisbury.
"And we cannot ignore the way that Russia seeks to undermine the international institutions which have kept us safe since the end of the Second World War."
Police cordons are still in place in Salisbury, a month after the poisoning that caused a diplomatic incident between the two countries.
Sergei Skripal remains critically ill but stable in his hospital while Yulia Skripal is recovering.
Karen Pierce said that a Russian request for consular access had been conveyed to Yulia, who is a Russian citizen, and "we await her response."
"We have received a request from the Russian consulate. We have conveyed it to Yulia Skripal and we await her response," she said.
"Ms Skripal's own wishes need to be taken into account."