One of YouTube’s most popular videos is pedalling a conspiracy theory about the deadly Parkland school shooting.

The post – currently at the top of YouTube’s “Popular Right Now” playlist – shows David Hogg, one of the Marjory Stoneman Douglas High School students who has led the push for gun reform in the wake of the shooting at the school. It suggests that he is an “actor”.

David Hogg struggles with interview questions in aftermath of Parkland school shooting

The video is part of a conspiracy theory that claims Mr Hogg and the other people representing themselves as students are actually paid actors, being used by gun control advocates to push for their policies. While the video simply re-posts an old video of Mr Hogg, its description says “DAVID HOGG THE ACTOR”, making clear why it is being uploaded and shared.

Florida shooting – in pictures Show all 10 1 /10 Florida shooting – in pictures Florida shooting – in pictures Police arrest a suspect in connection with the shooting at the Marjory Stoneman Douglas High School in Parkland, Florida Reuters Florida shooting – in pictures Parents wait for news after reports of a shooting at Marjory Stoneman Douglas High School in Parkland, Florida AP Florida shooting – in pictures Anxious family members wait for news of students AP Photo/Wilfredo Lee Florida shooting – in pictures Students being evacuated from the school AP Florida shooting – in pictures Students being evacuated from the school Getty Florida shooting – in pictures People gather waiting for word from students AP Florida shooting – in pictures Parents waiting for news on their children AP Florida shooting – in pictures People gather at a hotel where students were taken after the shooting Getty Florida shooting – in pictures Florida Governor Rick Scott speaks to the media as he visits Marjory Stoneman Douglas High School following the shooting AFP/Getty Florida shooting – in pictures Dr. Igor Nichiporenko, Medical Director Trauma, left, and Dr. Evan Boyer, Medical Director, Emergency Services, speak about treating victims and the suspect at a press conference outside Broward Health North hospital AP

The video is notable because it includes another time that Mr Hogg was part of a news story. It is a re-post of a news report about the fact that Mr Hogg had filmed a confrontation between a lifeguard and a surfer – and that the video he had uploaded had since gone viral.

That news story is entirely unconnected to the events at the Florida high school that left 17 people dead and many more injured. But conspiracy theorists are suggesting that it shows Mr Hogg is an actor who has been used to comment on news stories before.

It is just one part of that vast conspiracy, and other videos on the site include videos of Mr Hogg supposedly forgetting his lines while talking to camera and outright allegations that he is a “crisis actor”, and wasn’t actually an eyewitness to the shooting at all.

Many of those videos are recommended alongside the video about the lifeguard, meaning that anyone who sees it – potentially without context, after having clicked into YouTube’s most popular section – will be encouraged to watch more of the false conspiracy theory videos.

The YouTube playlist doesn't mean that it has received the most views of any video on the site – only that it is "trending", indicating that a lot of people are watching it and it is growing quickly.

But searching for Mr Hogg's name on the site shows a range of similar videos, many of them claiming that he is an actor and others offering supposed proof of that claim.

Mr Hogg has been forced to defend himself on CNN, after a tweet about the conspiracy theory was “liked” by Donald Trump Jr.

“I’m just so sorry that these people have lost their faith in America, because I know I certainly haven’t,” he told Anderson Cooper. He said it was “disturbing” to hear that he was being accused of being an actor, and said that he found it “unbelievable to me that people are saying this”.