FRANKFURT (Reuters) -- Porsche Chairman Wolfgang Porsche has gained majority support among the two clans that own his family's carmaker to remove cousin Ferdinand Piëch from his post as Volkswagen chairman, a German magazine reported this past weekend.

"It is not a question of 'if', rather 'when' and 'how'," Focus quoted one Porsche manager as saying.

The news magazine report ahead of its publication on Monday comes after a turbulent VW supervisory board meeting on Friday, where Piëch broke ranks with the other three Porsche representatives on the board.

Porsche had been quoted in comments made yesterday to Focus as saying of Piëch: "I am horrified by the behavior of the chairman."

The challenge is the result of long-running tensions between Piëch, part owner of Porsche, and his cousin over control of Volkswagen -- their company's largest investment in which the sports car maker is poised to take the majority this year.

Piëch, who has run Audi and Volkswagen as CEO before taking over as chairman in 2002, is a calculating strategist who has survived several coup attempts.

His power base stems from close allies like VW CEO Martin Winterkorn and the unwavering support from VW's powerful unions, which oppose Porsche's attempts to limit their influence.

Volkswagen declined to discuss the report while Porsche was not immediately available for comment.

On Monday, Lower Saxony Premier Christian Wulff urged squabbling factions at Volkswagen to stop their in-fighting at the German carmaker in which his state is the second-largest shareholder.

It would be "helpful if the strong personalities at VW ... talk to each other and approach each other", Wulff said on the sidelines of a meeting of his conservative CDU party on Monday.

But he acknowledged the situation could be defused only if the parties want to cooperate.

Wulff's appeal follows rare public discord among the extended Porsche and Piech clan which controls Volkswagen via a 31 percent stake -- soon to be raised to a majority -- and which owns sports car maker Porsche Automobil Holding AG.

Piech last week angered his cousin Wolfgang Porsche, chairman of the holding company which owns the stakes in the carmakers, by tacitly supporting VW workers eager to keep Porsche at arm's length.

Wolfgang Porsche was quoted as telling Focus magazine of Piech: "I am horrified by the behavior of the chairman".