"Whoever does not agree with such one-sided demands and wants to stand against them has the power of unions behind them in Germany, as per law," Birgit Dietze, the district leader for IG Metall in Berlin-Brandenburg-Sachsen, said.
Employees at Tesla's plant in Gruenheide, Germany, elected 19 people to its first workers' council in February, setting the plant apart from others run by the automaker in the U.S. and elsewhere without union representation, which Musk has fiercely resisted.
Some of the workers are part of IG Metall which represents workers across automotive companies and other industrial sectors.
In Germany there are currently no laws enshrining a right to work from home, but the labor ministry is working on policies that would increase flexibility for workers.
Many large employers, including automakers, have already embraced hybrid working models in the wake of the coronavirus pandemic which forced companies to send staff home to work.
"We have a fundamentally different view on creating an attractive working environment and stand for empowerment and personal responsibility in our teams to balance the ratio of mobile and in-person work," said Gunnar Kilian, Volkswagen Group human resources chief.