Porsche wants its investment in Volkswagen to generate a return of at least 10%, Porsche reportedly said on Tuesday following weekend news it planned to buy a 20% stake in VW.

"We expect a double-digit ROI on Volkswagen," a spokesman for the luxury carmaker told Reuters.

He reportedly added that Porsche would discuss with VW in the near future the purchase of the latter's own treasury shares that comprise 13% of the group's voting rights.

"We will also talk to VW about their treasury shares, but whether we can even get any of them or only just a portion of them is not clear," he told the news agency, adding that Porsche still has a stake of less than 5% in VW.

Reuters noted that Porsche has defended its plans to take a stake in Europe's biggest carmaker as a step it needs to ensure stable ties with a company that supplies content for 30% of its sales volume.