Robert Downey Jr.
Robert Downey Jr has been promoting his newest film, Avengers: Age of Ultron since early AprilJustin Tallis/AFP/Getty Images

Robert Downey Jr has spoken up about his awkward encounter with Krishnan Guru-Murthy earlier this month, labelling the Channel 4 presenter "a bottom-feeding muckraker" and "syphilitic parasite".

The 50-year-old walked out of an interview hosted by the journalist earlier this month, when he started probing Downey Jr about his personal life and dark past during what the actor thought would be a purely promotional piece about his latest film, Avengers: Age of Ultron.

Downey Jr grew more and more uncomfortable when Guru-Murthy started delving in to his history with substance abuse, but when the interviewer started asking about Downey Jr's relationship with his father, the actor decided enough was enough and abruptly cut short the segment, stating on his way out that it was "getting a bit Diane Sawyer".

On Howard Stern's radio show today (29 April), the Iron Man star stated: "I'm one of those guys who I'm always assuming the social decorum is in play, and that we're promoting a superhero movie, a lot of kids are going to see it, and that just has nothing to do with your creepy dark agenda."

Recalling how he felt during the interview, the Sherlock Holmes actor says he kept thinking: "You know what? You are weirding me out. I need to distance myself from this clown, otherwise I'm probably gonna put hands on this somebody and then there's a real story!"

He remembered: "My heart was beating in my chest because this was the first interview of the day. What do you think – are you in Kumbaya land?"

Aware that he was not the first celebrity to be upset by Guru-Murthy in a probing interview for the UK news, Downey Jr continued to say to Stern: "I don't even know that guy's name, but he pulled the same garbage on Tarantino.

"I'm a 50-year-old guy, I use fancy words and yet I'm completely unevolved when it comes to simple boundaries."

Downey Jr openly struggled with alcohol and drug addiction in the late 1990s, resulting in him being arrested several times for drug charges, during the years between 1996 and 2001. In 1999, he spent a year in California Substance Abuse Treatment Facility and State Prison and upon his release, managed to get his life back on track.

Whilst he starred in several titles after his stint in prison, appearing in films such as Zodiac, Kiss Kiss Bang Bang and Gothika, he was propelled back into established Hollywood fame when he landed the role of Tony Stark (Iron Man) in the first Marvel movie surrounding the character back in 2008.

Meanwhile, despite the backlash he got on social media for the interview, Guru-Murthy defends the fact that he attempted to get some more personal information out of his guest stating: "We don't do promotional interviews on Channel 4 News. We agree with PR people that as well as talking about a new movie for a while we want to ask wider-ranging questions on relatively serious topics, and we don't guarantee to run any answers in particular."

Downey Jr eluded to his fraught interview with Guru-Murthy by sharing a photograph of him and Diane Sawyer making reference to it being "legitimate journalism"Instagram