Democratic US Senator Elizabeth Warren sent a letter to Tesla's board on Monday questioning whether Elon Musk is meeting his legal obligations to the car maker and its shareholders following his purchase of Twitter.
Ms Warren wrote that Mr Musk’s actions at the helm of Twitter have “raised questions about possible violations of securities or other laws”.
“Despite widespread concerns about Mr Musk’s acquisition of Twitter while serving as CEO of Tesla, it remains unclear whether the Tesla board — which has key decision-making authority within the company — is adequately governing the company or if it has established clear rules and policies to address the risks to Tesla posed by Mr Musk’s dual roles,” Ms Warren wrote.
Mr Musk has pulled Tesla engineers away from the electric car company to help out at Twitter since he bought the platform for $44 billion earlier this year.
The senator’s letter also raised concerns about whether there is a conflict of interest between his roles at Tesla and Twitter, particularly because Tesla competitors such as Audi AG advertise on Twitter’s platform.
The Tesla chief was uncharacteristically quiet on Twitter on Monday, a day after he asked users if he should step down from leading the company.
He had promised to abide by the results of the poll but had made no comment as of 1.45pm ET.
Mr Musk's takeover of Twitter has been disastrous for Tesla stockholders, who this year have seen the car maker lose more than 60 per cent in value as he has tweeted right-wing political views, alienating a large chuck of his liberal customer base.
Dan Ives, managing director of Wedbush Securities, said the end of Mr Musk's reign as Twitter chief executive would be “a major positive for Tesla’s stock starting to slowly remove this albatross from the story”.
“Time to end this nightmare as CEO of Twitter,” he wrote.
Bloomberg contributed to this report