New registrations of Tesla cars in Sweden increased in December from a year earlier and the car maker's market share grew, industry data showed on Tuesday, despite union action against the company hampering imports.

Data from Swedish auto industry association Mobility Sweden showed 1,789 new Tesla cars were registered in December, up from 1,645 in the same month of 2022. The U.S. company's market share grew to 6.1% from 4.6%.

Tesla is facing a wave of union action in the Nordic region, backing Swedish union IF Metall's mechanics who went on strike in October, demanding a collective agreement covering wages and other conditions.

Dock workers in Sweden and Denmark have in sympathy action stopped unloading and transporting Tesla cars destined for Sweden.

Tesla's Model Y was Sweden's top-selling car in 2023 with 16,412 new vehicles registered, ahead of Volvo's XC40 with 13,606 cars.

But in December, the Model Y slipped to fourth place with 1,098 new cars registered, lagging the XC40's 1,967 cars. (Reporting by Anna Ringstrom, editing by Terje Solsvik)