Russian UN ambassador Vassily Nebenzya, speaking at the UN Security Council in New York, said the UK has questions to answer.
He added: "We have told our British colleagues that you are playing with fire and you will be sorry."
Mr Nebenzya, whose speech was transmitted in English via an interpreter, earlier said: "Everyone who knows crime novels, for example, the Midsomer Murders - a well-known British series - they all know hundreds of very clever ways of killing someone.
"However, those who sought to kill Sergei Skripal and his daughter supposedly chose an extremely toxic chemical substance, the most risky, dangerous method possible.
"At the same they didn't really finish the job because the two individuals seem to be alive and Yulia, thank God, seems to be improving rapidly.
Mr Nebenzya mockingly referred to Prime Minister Theresa May and Foreign Secretary Boris Johnson as "expert chemists", later saying the UK's main argument about the "unquestionable Russian origin" of the Novichok is "no longer valid" following comments from Porton Down's Gary Aitkenhead.
Mr Nebenzya said Novichok is "not copyrighted by Russia, in spite of the obviously Russian name" and said it was developed in "many countries".
"You're playing with fire and you'll be sorry" Russian Ambassador to the UN tells Britain pic.twitter.com/JcYkg9vuIk— Sky News (@SkyNews) April 5, 2018
He criticised the sources of the British intelligence services, saying reports that Russia had tested Novichok before the attack on everyday objects was "some sort of theatre of the absurd".
Mr Nebenzya went on: "Couldn't you come up with a better fake story? We all know what the worth of British intelligence information is based on the experience of Tony Blair.
"We have told our British colleagues that you're playing with fire and you'll be sorry."
Mr Nebenzya said: "Using the media, it is easy to manipulate human consciousness. We are witnessing how the Western media is very successful at doing this.
"This is all using the method of Dr Goebbels - lies that are repeated a thousand times become the truth.
"We will demand answers from you to the questions we have put, and if you don't provide answers, if you don't agree to answers we will then consider this as evidence of slander which you have used against us.
- Press Association and Digital Desk