The question from the audience was “how certain are you that the Salisbury attack was beyond doubt the responsibility of the Russian state?”
Sir Keir Starmer said that Theresa May was correct in expelling Russian diplomats in response to the attack.
Pointing to Keir Starmer, Mr Rattansi continued: “This person to my right who has had close contact with the intelligence services says ‘only Russia had these chemicals’.
“That’s something, given that Britain vetoed in the past few hours a UN Security Council resolution asking for an investigation into these atrocities in Wiltshire.
“Why did Britain veto that resolution? That’s interesting, isn’t it?
“Why is it that neo-con, neo-liberal Labour Party members continue to try and use WMDs to push us into war. That is an implication, certainly, over what your leader Jeremy Corbyn has been saying.”
An exacerbated David Dimbleby interrupted, saying: “I’m sorry, we’re getting off the point. You were asked a very simple question by Paul Wilson, do him the honour of answering his question.
“‘How certain are you that the Salisbury attack was beyond doubt the responsbility of the Russian state?’”
But an un-ruffled Rattansi coolly replied: “Even the Prime Minister said it was only highly likely, so it is not beyond reasonable doubt. We must have an urgent investigation.”
Mr Dimbleby hit back: “And you?”
The RT presenter said: “I really don’t know. And in a sense, RT as a channel, going underground, we try and look at certainty and question more.
“We cannot believe our Governments anymore like we used to, just because a Prime Minister stands up and says, ‘the security services have told us so.’
“Those days are over.”
There was controversy around inviting Mr Rattansi on the panel because of his involvement in Russian state TV with Conservative MP for Totnes Sarah Wollaston saying she hoped other panellists “walk out in disgust”.
But Mr Rattansi did not roll over, responding to the question he said: “Obviously everyone condemns this attack, it’s terrible for the police officer and these two spies.
“And can I just say thank you to the BBC for inviting me because the head of the liaison committee in Parliament, Sarah Wollaston MP, has told all the people on this panel to walk off.
“That’s free speech in this country.”
Labour’s Sir Keir Starmer responded: “I have not had a conversation with her, she has not spoken to me.”
But Mr Rattansi replied: “She has tweeted that the entire panel should walk out, I never said she had spoken to you.”
Vladimir Putin and Russian officials have maintained it had no hand in the poisoning, which left former double agent Mr Skripal and his daughter Yulia in a critical but stable condition in hospital.
But the UK is to expel 23 Russian diplomats as a response to the poisoning.
Britain is supported by the US, Canada, France and Germany in its accusation of Russian involvement in the poisoning.