Sara Firth, a longstanding London-based correspondent for Russia Today, resigned on Friday in protest at the channel's coverage of the Malaysia Airlines crash.
Firth, who joined the channel in 2009, told BuzzFeed that she decided to resign from the Kremlin-funded news channel because she felt it was "disrespectfully" attempting to pin the blame for Thursday's Malaysia Airlines disaster on the Ukrainian government.
"When this story broke I ran back into the newsroom and saw how we were covering it already and I just knew I had to go," she said.
"It was the total disregard to the facts. We threw up eyewitness accounts from someone on the ground openly accusing the Ukrainian government [of involvement in the disaster], and a correspondent in the studio pulled up a plane crash before that the Ukrainian government had been involved in and said it was 'worth mentioning'.
"It's not worth mentioning. It's Russia Today all over, it's flirting with that border of overtly lying. You're not telling a lie, you're just bringing something up. I didn't want to watch a story like that, where people have lost loved ones and we're handling it like that.
"I couldn't do it any more. Every single day we're lying and finding sexier ways to do it."
Russia Today has been hit by high-profile staff resignations before, most spectacularly when anchor Liz Wahl resigned live on air earlier this year.
Firth, a Briton who graduated from City University in 2009, worked out of the news channel's Moscow base initially, before coming to work in London. She claims that inexperienced staff would be assigned to important stories in order to ensure they did not go off-message.
"The way it works with a story like this is that the people who are assigned are very obedient. The second you start to question or report honestly then you're a problem.
"The first thing that happens is that they assign the usually least experienced in RT, the second is everyone else who's involved [starts] phoning guests that have a particular viewpoint and are going to say a particular thing."
While many journalists are attracted to Russia Today by healthy salaries and the prospect of a secure job, Firth said there was a belief there that you could stay "within the system and fight against the bad forces".
She insists she never lied in any of her reports but became concerned about the airtime given to her journalism and was concerned that her reports were "lending credibility" to the channel's other output. She alleges she was pulled out of Syria by channel bosses the day after filing a report highlighting the suffering of civilians in areas opposed to the Assad regime, which is backed by Russia's president, Vladimir Putin.
Firth said she had immense respect for her "talented" colleagues and said the vast majority of journalists at the channel were working hard to tell the truth, but that the management "ignore that and push the rubbish".
"It's great team, so talented. But at the heart of that organisation it's rotten. Until they have people operating at the top level who want to tell the truth and tell the facts then it's not going to change."
"There is a perception of RT as an evil genius but it's actually just dangerous incompetence."
Russia Today has been contacted for comment.
Anna Belkina, head of communications at Russia Today, has provided the following statement:
"We were not surprised by Sara Firth’s decision to leave RT after 5 years as a Moscow and London correspondent, as she has recently informed us that she was likely to take an offer from another firm."
"The plane crash is an absolutely terrible tragedy, there are a lot of questions that surround it and everybody is looking for answers. More than 15 RT journalists are working on this story – from Moscow, from the Russian-Ukrainian border, London, Berlin, Washington. RT Spanish journalist Francisco Guaita was one of the first TV correspondents to get to the scene late last night. Our reporters are in the Netherlands and Malaysia."
"Sara has declared that she chooses the truth; apparently we have different definitions of truth. We believe that truth is what our reporters see on the ground, with their own eyes, and not what’s printed in the morning London newspaper. In our coverage, RT, unlike the rest of the media, did not draw conclusions before the official investigation has even begun. We show all sides of the story, even if everyone else has already decided which side is to blame."