Milton will be replaced by board member and former General Motors Co. vice chairman Stephen Girsky, effective immediately.
“The focus should be on the Company and its world-changing mission, not me,” Milton said in a letter to employees. “I intend to defend myself against false allegations leveled against me by outside detractors.”
Milton’s resignation comes 10 days after short-seller Hidenberg Research accused Nikola of being an “intricate fraud” that mislead partners about its technology, causing both the U.S. Securities and Exchange Commission and Department of Justice to launch investigations.
Nikola called the claims “false and deceptive.”
Hindenberg’s report was released on Sept. 10, two days after Nikola and General Motors announced a partnership that gave GM a $2 billion stake, or 11% of Nikola, in exchange for its help building the Badger electric-pickup truck.
General Motors stood by its partnership with Nikola, saying on Monday that it plans to work toward closing the transaction while also noting the deal is just part of its EV strategy. GM CEO Mary Barra last week said the U.S. auto giant performed “appropriate diligence” before entering into the deal.
As GM defended the partnership, Milton bought an additional 41,400 shares, raising his stake to 91.6 million shares, or about 25% of the company. All of his wealth is tied to the company, according to Forbes.
Nikola shares have been on a rollercoaster ride this year.
They soared as much as 179% in its first five days of trading, putting in a high of $93.99 before on June 9 before sliding by 69% through the end of July to $29.06.
Shares finished at $33.97 apiece on Friday, up 0.65% from where they began trading on June 3.