New Delhi, Feb. 18 -- Germany's biggest union is accusing Tesla Inc. of fostering a toxic working environment at the carmaker's factory near Berlin, as tensions mount ahead of a contested works council election.

The US manufacturer is overworking employees and putting pressure on staff that have fallen ill, IG Metall said Wednesday. The union applied for an injunction at a labor court over what it said were false allegations that one of its members recorded a works council meeting on a laptop. It asked prosecutors to investigate a local Tesla manager for defamation.

Tesla's management is attacking unions in Germany "with unprecedented aggression," said Jan Otto, a regional IG Metall leader. "The company must not be allowed to get away w...