The UK has accused Moscow of "playing fast and loose with the institutions that protect us"
Britain has been warned by Russia it is "playing with fire and will be sorry" over the Salisbury nerve agent attack.
A special meeting of the UN Security Council on Thursday night was called by Russia.
Moscow's UN ambassador Vasily Nebenzya opened the session by asking why viewers of the British TV programme Midsomer Murders would believe Russia chose "the most risky and dangerous method" to kill two of its citizens.
"They all know hundreds of very clever ways of killing someone," he declared.
Mr Nebenzya praised the chief executive of the UK's Porton Down laboratory, who said this week that scientists had not yet discovered the "precise source" of the nerve agent used in Wiltshire last month.
"He did not pay tribute to the guesswork put forward by British security services," the ambassador said, adding that the novichok substance identified "is obviously not copyrighted by Russia".
Mr Nebenzya said British officials were "playing with fire" - and warned: "You'll be sorry."
He then likened the media to a "psychotropic substance" and the western coalition that expelled diplomats to Nazi propagandist Joseph Goebbels.
He concluded: "The investigation is far from being over, in fact it has only just begun."
British ambassador Karen Pierce said she would take no lectures from Moscow and would "stick to the facts".
She compared Moscow's demand to be included in the investigation of Sergei and Yulia Skripal's poisoning to "an arsonist trying to investigate his own fire", and insisted the British allegations would stand up to scrutiny.
She defended the British Foreign Secretary Boris Johnson, saying there was "no contradiction" in saying Porton Down officials had "no doubt" when asked why he was sure the nerve agent originated in Moscow.
"The Foreign Secretary was making clear Porton Down is sure the nerve agent was a novichok," she said.
"The threats to the chemical weapons convention, in Syria, in Malaysia and now the UK, place a very serious challenge to the non-proliferation regime that this organisation has constructed in response to the terrible events of the past.
"Russia is playing fast and loose with the institutions that protect us."
US ambassador Kelley Currie followed up by attacking Russia's comparison of western states to Goebbels, saying it was "not a tactic appropriate for this body".
She also accused Mr Nebenzya of "using this chamber to undermine the truth".
The emergency session came hours after Yulia Skripal issued her first statement on the attack, saying her "strength is growing daily".
She said: "I am grateful for the interest in me and for the many messages of goodwill that I have received.
“I have many people to thank for my recovery and would especially like to mention the people of Salisbury that came to my aid when my father and I were incapacitated."
She added: “I am sure you appreciate that the entire episode is somewhat disorientating, and I hope that you’ll respect my privacy and that of my family during the period of my convalescence.”
The international chemical weapons watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), is expecting to receive results from tests of samples from Salisbury next week.