Already tension and hostility between two of Germany's most important carmakers is reaching the boiling point. Boardroom dramas and stock acquisitions have supplanted spy scandals as Porsche continues its takeover of Volkswagen, and the latest development involves VW building barriers between Porsche and its internal operations.

Central to the new policy is a document drafted by VW's lawyers effectively placing a wall around the company's activities, specifically designed to keep Porsche from having any knowledge of or influence on its day-to-day dealings. The only thing VW must disclose is information necessary to compile financial statements.

Other internal information that might be costly to VW should Porsche become aware of it will only be made available to the maker from Stuttgart if it pays VW for the projected disadvantage - effectively charging the opportunity cost of keeping the information secret, reports Automotive News Europe. Any contracts signed with Porsche will accordingly be treated as if they were done with third parties, rather than a substantial shareholder.

Porsche has refused to make any statement on the latest development in the ongoing power struggle between the companies, but it obviously will only make it harder to extract value from its acquisition of the VW Group's shares. Still, with the value of the stock rising - up 9.1% in trading on Wednesday - despite the internal turmoil, Porsche's investment will likely pay off with or without VW's cooperation.

Earlier this month talk of a possible collaboration between VW and Porsche on an all-new 914 stirred enthusiasts' desire around the world, but such amicable arrangements appear to be unlikely at the moment.