"Everyone at Tesla is required to spend a minimum of 40 hours in the office per week," he wrote in one of the emails. "If you don't show up, we will assume you have resigned." Mr Musk said working in the office full-time was what the company asks of its factory employees and in-person collaboration was critical to the firm's success. "There are of course companies that don't require this, but when was the last time they shipped a great new product? It's been a while," he said in an email, one of two that was leaked and shared on social media.