Europe's largest carmaker is considering either a minority holding in Proton, the owner of UK sports-car manufacturer Lotus, or a controlling stake to tap demand in growing southeast Asian markets, sources told Reuters in July.

VW, which surpassed Toyota last year to become the world's second-biggest car maker, has been scooping up brands including Scania, MAN, Porsche and Ducati in recent years as part of an effort to overtake General Motors at the top of the industry by 2018.

"We already have 12 brands and we first have to stabilise the group," Bernd Osterloh told Handelsblatt in an interview to be published in the paper's Monday edition.

"Even though further sales and production sites in south-east Asia are important, there is no support from the labour side for a purchase of Proton."