Fifteen black former or current employees at Tesla have filed a lawsuit against the electric carmaker, alleging they faced racial abuse and harassment at its factories.

The workers said they were subjected to offensive racist comments and behaviour by colleagues, managers, and human resources employees on a regular basis, according to the lawsuit filed in a California state court.

The harassment, which allegedly occurred mostly at Tesla’s Fremont factory in California, included using the N-word and terms such as “slavery” or “plantation” or making sexual comments, the lawsuit claims. It alleges that the automaker’s “standard operating procedures include blatant, open and unmitigated race discrimination”.

Some of the plaintiffs were assigned to the most physically demanding posts in Tesla or passed over for promotion, according to the lawsuit.

It said that Montieco Justice, a production associate at Tesla’s Fremont factory, was immediately demoted upon returning to Tesla after taking an authorised leave of absence as a result of contracting Covid-19.

Tesla did not immediately respond to a request for comment.

The automaker is facing at least 10 lawsuits alleging widespread race discrimination or sexual harassment, including one by a California civil rights agency.

It previously has denied wrongdoing and says it has policies in place to prevent and address workplace misconduct.

On Monday, a federal judge in California ordered a fresh trial on the damages Tesla owes to a black former factory worker who accused the company of race discrimination, after he turned down a $15m (£12.4m) award.

This month, a Tesla shareholder filed a lawsuit accusing the chief executive, Elon Musk, and the company’s board of directors of neglecting worker complaints and fostering a toxic workplace culture.