The journalist who interviewed the two Russians suspected of the Salisbury Novichok attack hung up on a BBC presenter after "the manner of the interview" was challenged.
Speaking to BBC Newsnight exclusively about her television interview with Alexander Petrov and Ruslan Boshirov, RT editor-in-chief Margarita Simonyan, said: "I don't have any reasons to believe these people either. But I have even less reasons to believe the British secret services".
In the interview on the state-run RT channel, the pair said they had travelled to Salisbury on the recommendation of friends.
Downing Street described these claims as "lies and blatant fabrications".
When questioned by Kirsty Wark about whether RT was a propaganda tool for the Russian State, Ms Simonyan said: "Your question to me seems like typical Western propaganda."