A Russian MP was cut off the air after he compared Britain's conduct to that of Adolf Hitler, as the UK accused Moscow of being responsible for the nerve agent attack on a former spy in Salisbury.
Vitaly Milonov, from the United Russia party, accused the UK of being behind a "fantasy" operation involving the poisoning of former double agent Sergei Skripal and his daughter, Yulia.
He described as "fake news" the claim from Theresa May that it was "highly likely" Russia was behind the attack, saying it was nothing to do with Moscow.
Speaking on BBC Radio 4's Today programme, Mr Milonov said: "My personal point of view [is] that Theresa May and her colleagues they have created a fake story because they need an explanation to British people and British business why they are going to perform some anti-British steps in favour of United States policy against Russia.
"So, they had to make this fantasy. They had to kill, to try to kill, this poor pensioner, useless for us.
"This is a drama for British TV. It's a behaviour of Hitler when he blamed someone in burning of Reichstag."
He was then taken off the air after Sarah Montague, the show's host, asked: "So the UK Government is behaving like Hitler?"
Earlier, Mr Milonov had branded Mr Skripal a "useless fake agent".
When he was asked how the nerve agent came to Britain, Mr Milonov said: "This poison is 50 years old, it's not modern stuff. You can take this poison from any laboratory in Ukraine or other fake countries that are happy to help you."
The Russian MP compared the situation to being like a James Bond movie, saying: "You created such a horror about new Russia which is very dangerous. For us this guy is absolutely useless."
His comments came after Russia's foreign minister told Ms May Moscow "is not to blame" for the military-grade nerve agent attack on Mr Skripal.
Sergei Lavrov said Russia was willing to cooperate with the probe, but suggested the UK would be “better off” complying with its international obligations “before putting forward ultimatums."
Ms May said Russia has until the end of Tuesday to explain how the substance ended up in Britain.
Officials said the Prime Minister was reviewing a range of economic and diplomatic measures in retaliation for the assault.