Elon Musk has decried a wave of “insane” strikes focused on Tesla workshops in Sweden, as workers target the US electric car manufacturer in a strike calling for collective bargaining rights.

In what has been portrayed as the largest fight in decades to save Sweden’s union model from global labour practices, the powerful trade union IF Metall has been leading a strike across eight Tesla workplaces in Sweden for five weeks.

It is the first time workers for the US carmaker have gone on strike and on Thursday, Musk, the tech billionaire and chief executive of Tesla, made his feelings clear, writing on X, formerly Twitter: “This is insane.”