Tesla shares have dropped sharply after the company’s accounting chief quit after just weeks in the job and chief executive Elon Musk appeared to smoke marijuana during an interview.

In the interview streamed live on YouTube on Friday [local time], Mr Musk smoked a cigarette that the host, comedian Joe Rogan, said was a mixture of marijuana and tobacco.

“You want some, man?” Rogan asked during the lengthy two-and-a-half hour interview. “You probably can’t because of stockholders, right?”

“I mean, it’s legal right?” said Mr Musk before taking the cigarette from Rogan and inhaling.

The interview was recorded in California where marijuana has been legalised for medical and recreational use.

Elon Musk smoking a blunt for the first time on Joe Rogan's podcast is Internet gold https://t.co/nx8zQ7HlyB

— Gifdsports (@gifdsports) September 7, 2018

In the hours of trading on Friday morning, shares in the electronic car company were down 9 per cent, falling to $US254 ($357) from their earlier high of $US302 ($424) last Friday.

The video of Mr Musk smoking marijuana came after the shock resignation of Tesla’s chief accounting executive after just one month in the job and amid mounting concerns over the tycoon’s behaviour.

In a statement to the US Securities and Exchange Commission on Friday, it was announced accounting chief Dave Morton had tendered his resignation less than a month after joining Tesla, citing concerns about the pace of the company and the level of public attention.

Mr Morton joined Tesla just days before Mr Musk announced on Twitter that he was taking the company private.

“Since I joined Tesla on August 6, the level of public attention placed on the company, as well as the pace within the company, have exceeded my expectations,” Mr Morton said in a statement.

“As a result, this caused me to reconsider my future. I want to be clear that I believe strongly in Tesla, its mission, and its future prospects, and I have no disagreements with Tesla’s leadership or its financial reporting.”

Tesla’s head of human resources, Gabrielle Toledano, also told Bloomberg News she will not be rejoining the company after a leave of absence.

Tesla shares have lost one-third of their value since August and nearly a dozen top executives have left the company, sparking questions about Mr Musk’s fitness to run both Tesla and aerospace company, SpaceX.

The Tesla tycoon says his sometimes wacko tweets have nothing to do with drug use.

In an interview with The New York Times in August, the 47-year-old detailed the “excruciating” personal toll of running Tesla.

The company has been beset by manufacturing delays and is now the subject of a federal investigation after Mr Musk announced in an August 7 tweet his plan to make the company private, sending Tesla shares soaring.

“This past year has been the most difficult and painful year of my career,” he said, revealing he often worked 120-hour weeks and his wellbeing was starting to fray.

The tweet and subsequent investigation have ignited tensions within Tesla’s board, the Times wrote, and concerns about Mr Musk’s use of the prescription anti-insomnia drug, Ambien.

“It is often a choice of no sleep or Ambien,” Mr Musk said.

In the interview with Rogan, the father-of-five who has cemented himself as one of Silicon Valley’s most ambitious entrepreneurs, said his mind was like “a never-ending explosion” and that it was very hard to turn his brain off.

“I don’t think you’d necessarily want to be me,” he said. “I don’t think people would like it that much.”

The image of Mr Musk smoking marijuana quickly began circulating on Twitter, sparking memes based on his recent controversial comments, including calling a Thai cave diver who rescued a trapped soccer team a “pedo”.

*Elon musk takes a long drag on a joint*
"If you really think about it, all divers are paedophiles"

— TechnicallyRon (On all the platforms) (@TechnicallyRon) September 7, 2018

What if we sent the cave kids… to Mars? pic.twitter.com/kLxS9tWepS

— southpaw (@nycsouthpaw) September 7, 2018

https://twitter.com/redsteeze/status/1038076611927654400