COPENHAGEN (Reuters) -Sweden's largest insurer Folksam said on Wednesday it has sold its stake in electric car maker Tesla over concerns about the company's stance on workers' rights.

Tesla, headed by billionaire Elon Musk, is facing a backlash from unions and some pension funds in the Nordic region over its refusal to accept a demand from Swedish mechanics for collective bargaining rights covering wages and other conditions.

Tesla did not immediately respond to a request for comment. The company has said it offers as good, or better, terms than those demanded by the unions.

Folksam said in a statement it had tried to influence Tesla, together with other owners, through proposals submitted to the company's annual general meeting two years in a row.

"Unfortunately, no improvement has been seen and a decision has therefore been made to divest the holding," its head of asset management and sustainability Marcus Blomberg said.

Folksam's holding amounted to 0.017% of Tesla and had a market value of 1.6 billion Swedish crowns ($159.98 million) at the time of divestment, a spokesperson said.

($1 = 10.0015 Swedish crowns)

(Reporting by Stine Jacobsen, editing by Terje Solsvik and Louise Heavens)