By Matthew Field

Elon Musk has told Twitter staff to embrace an “extremely hardcore” working culture or leave the company by Thursday.

In a midnight email to workers, the Tesla billionaire set out his vision for “Twitter 2.0”, saying that to “succeed in an increasingly competitive world, we will need to be extremely hardcore.”

“This will mean working long hours at high intensity,” he wrote. “Only exceptional performance will constitute a passing grade.”

The billionaire attached a form to his email asking staff to accept a new employment contract, adding: “Anyone who has not done so by 5pm ET tomorrow (Thursday) will receive three months severance.”

The Tesla and SpaceX chief executive is known for his own punishing work routine, which at one stage included living in a Tesla factory and sleeping on the factory floor. He has already cancelled Twitter’s working from home policy and ended its free lunches since taking over in a $44bn (£37bn) buyout in October.

The ultimatum to staff could prompt a further flood of exits at Twitter, which has already shed thousands of staff in mass redundancies and sacked a reported 80pc of its contractor workforce.

The billionaire has insisted the cuts are to make Twitter lean and competitive, and previously argued the company was overstaffed and inefficient. On completing the takeover, he immediately fired a clutch of senior executives and dismissed the company’s board.

He has also fired a number of staff for dissent, including one Twitter engineer who was informed he was fired in a public exchange of messages on the social media website.

Mr Musk has unveiled sweeping changes as he seeks to improve revenues and cut costs at the company. Twitter faces more than $1.2bn in interest payments over the next 12 months on the $13bn of debt Mr Musk used for his buyout of the company.

Changes announced so far include launching a paid subscription version of the website, as well as ditching entire teams responsible for maintaining parts of the social network.