Two of Germany's most important carmakers are at odds over who will control day-to-day operations once a planned stock acquisition is completed.

Just over a week ago, Volkswagen called on Porsche to make it clear that it wouldn't interfere with VW's daily operations once it becomes the auto giant's largest shareholder, and VW chairman Ferdinand Piëch broke ranks with his Porsche-family cousins to side with VW. Now the latest reports claim that a coup is brewing in Stuttgart, and Piëch is the target.

The power struggles between the two companies have been underway and tensions have been building for nearly two years, ever since speculation about Porsche's intent to acquire a majority interest in VW began to mount. VW's CEO Martin Winterkorn has even threatened to resign if the Porsche takeover moves forward.

German news source Focus is now reporting that Porsche executives are working on a plan to get Piech out of his position on VW's board and Wolfgang Porsche himself may be spearheading the plan. His reaction to Piech's decision to side with VW certainly provoked a negative reaction in Porsche. "I am horrified by the behavior of the chairman," he said.

A number of scandals including a spy incident involving a baby monitor have stepped up the level of concern in both camps over the past year, and to date the two companies have reached no formal agreement on how power will be shared or which directors and executives will have final control. This latest development, if it proves to be true, could spell the end of niceties between the two companies. That would be unfortunate, however, as there is much good that could come of a Porsche-VW partnership, not the least of which is the revival of the 914.

Synergies between the two companies already exist, with VW facilities producing chassis, bodies and other components for the current Cayenne and future 2010 Panamera. Porsche isn't entirely happy with the arrangement, however, due to what it perceives as substandard quality in early Panamera bodies. VW is quick to counter with the defense that the current run is still 'practice' and that the final production examples will be top-notch, reports Automotive News Europe.

Tensions aren't building solely at the executive level, either. Union workers are nervous that Porsche's takeover could mean lower wages and massive job cuts. IG Metall, a German union that represents about 90% of VW's workers, is already in the midst of a dispute with Porcshe CEO Wendelin Wiedeking over the luxury sports car maker's desire to have an equal number of staff representatives to VW in the holding company that will be used to purchase the VW shares - despite the fact that VW employs about 20 times more workers than Porsche.

The German state of Lower Saxony has made clear its intent to hang onto a 20% minority stake to defend the interests of its workers and the VW factories within its borders. Thanks to a law known as 'the VW law' that 20% interest allows the state to block action by a simple majority shareholder in certain circumstances.