BERKELEY, California, July 6 (Reuters) - Shareholders of Nikola Corp (NKLA.O) have voted against a proposal to approve compensation paid to its "named executive officers," including $159.2 million to founder and former executive chairman Trevor R. Milton, the electric truck maker said on Tuesday. The decision, although non-binding, illustrates shareholders" discontent about Nikola, once a high-flying company whose shares tanked over 80% from its peak partly due to ongoing probes by regulators and prosecutors. The compensation, which includes salary, bonus and stock awards, was proposed to a total of six people, including chief executive officer and president Mark Russell with $159.2 million and Britton Worthen, chief legal officer with $79.6 million. The shareholders" meeting took place on June 30. Nikola and some of executives are facing a series of class action lawsuits, which allege they made false and/or misleading statements regarding Nikola"s business plan and prospects.