Cayenne models are parked at the Porsche plant in Leipzig, June 2, 2009. REUTERS/Tobias Schwarz

FRANKFURT (Reuters) - A majority of members in two families controlling Porsche PSHG_p.DE back a deal for the Gulf state of Qatar to acquire a 25 percent stake in the German luxury carmaker, Der Spiegel magazine said.

It said Qatar and adviser Credit Suisse have already completed their due diligence on June 8.

The Porsche and Piech families own the common shares in the company and have so far never allowed outsiders to acquire any of it.

Der Spiegel said Porsche chief executive Wendelin Wiedeking’s timetable would be for the Porsche supervisory board to hold a special meeting in early July to approve a capital increase.

Porsche shareholders would then approve the capital hike in a general shareholders meeting in early September so that 4-5 billion euros ($5.63 billion) in new money could be raised by November at the latest.

The new capital could help lift Porsche SE's balance sheet, which is saddled with nine billion euros of net debt it had incurred to pave the way for the now aborted plan to take over Volkswagen VOWG.DE.