Tesla stock is on course for its worst week since the onset of the pandemic in March 2020, losing $80bn in market value, in a reflection of investors’ deepening doubts about the electric carmaker’s prospects as CEO Elon Musk runs Twitter at the same time.

Shares in Tesla hit their lowest point in more than two years on Friday, taking its market capitalisation below $400bn. The stock has lost 17 per cent this week.

Tesla was worth $1.2tn at the beginning of the year. The drop of more than $800bn in value is equal to the combined current market capitalisation of more than 80 of the smallest companies in the S&P 500 index, according to S&P Global Market Intelligence. This week’s Tesla’s market cap slipped below that of ExxonMobil, a company reliant on fuelling internal combustion cars.

Downward pressure on Tesla’s stock has intensified in recent months because of the combination of Musk’s own heavy selling to fund his $44bn takeover of Twitter and mounting concerns about the outlook for sales of its electric cars.

Tesla’s share price dropped 9 per cent on Thursday after the carmaker said that it would offer price discounts of $7,500 to US consumers on two of its best-selling models, an announcement that has fuelled worries over consumer demand.

Later that day, Musk promised via Twitter he would not sell any more of his Tesla stake for at least a year. He also said he was open to the idea of buybacks.

“I won’t sell stock until, I don’t know, probably two years from now. Definitely not next year under any circumstances and probably not the year thereafter,” he said.

Musk, who recently lost the position of world’s richest man, has sold almost $23bn of stock since announcing his $44bn acquisition of Twitter. Despite a promise in April to stop doing so, he subsequently sold shares on three occasions, most recently last week. The disposals have angered big investors who feel the entrepreneur has abandoned the carmaker to focus on Twitter.

Musk has promised to step down as chief executive of the social media platform, once he finds a replacement, following a poll of Twitter users on Sunday on the issue.

Wedbush Securities tech analyst Dan Ives, on Friday lowered his price target from $250 to $175 for the shares but maintained an “outperform” rating. Tesla’s stock was 0.5 per cent lower at $124.69 at mid-afternoon on Friday.

Ives tweeted: “We believe if Musk refocuses back on Tesla, truly stops selling stock (walk the walk, not just talk the talk), the Board initiates a buyback, and 2023 guidance is set conservative on its [fourth-quarter] call in January then this stock has bottomed in our opinion and works from here.”

Of the 41 Tesla-following analysts tracked by Refinitiv, four have “sell” ratings on the stock.

The drama surrounding Musk has helped make Tesla the most profitable US company for short sellers this year, delivering paper profits of just over $15bn in 2022, according to S3, a specialist New York-based consultancy. Short sellers aim to profit from share price falls.

Since August, short sellers have increased their total short positions in Tesla by about a third to 81.8mn shares, or just over 3 per cent of the carmaker’s outstanding stock in a wager that is worth roughly $11.3bn, S3 calculated.