Russia has accused the UK of inventing a “fake story” and “playing with fire” over the Salisbury spy poisoning.
Moscow’s UN ambassador Vasily Nebenzya told a meeting of the UN Security Council: “We have told our British colleagues that you are playing with fire and you will be sorry.”
The UK claims Russia is behind the attack. Russia denies responsibility.
Russian former spy Sergei Skripal and his daughter Yulia were found unconscious in Salisbury on 4 March.
Ms Skripal, 33, is recovering in hospital and has released a statement saying her “strength is growing daily”.
Her father, 66, remains critically ill but stable.
Moscow called the special meeting of the Security Council in New York to discuss the attack, saying Britain had “legitimate questions” to answer.
Mr Nebenzya called the accusations “horrific and unsubstantiated” and accused the UK of waging a “propaganda war” against Russia.
He said Novichok – the group of nerve agent used in the poisoning – is “not copyrighted by Russia, in spite of the obviously Russian name” and has been developed in many countries.
He criticised the UK’s intelligence services and, responding to reports that Russia had tested the chemical on everyday objects prior to the attack, said: “It’s some sort of theatre of the absurd.”
“Couldn’t you come up with a better fake story?” he asked.
“We all know what the worth of British intelligence information is based on the experience of Tony Blair,” he said, referring to the findings of the Chilcot Report that the former UK prime minister’s invasion of Iraq in 2003 was based on “flawed” intelligence.