Volkswagen Group chief executive Martin Winterkorn has said that if Porsche interferes with the day-to-day running of Volkswagen, then Wendelin Wiedeking might as well take over as chief executive himself.

The comments are a further escalation in the power struggle between Volkswagen's largest shareholder and representatives of the Volkswagen Group, which are concerned that effective management control will move to the Porsche Holding company, when it acquires enough shares to take majority control of the company by the autumn. In the past the Volkswagen workers' representatives have had a major input into management decisions and their support has been crucial to shaping the direction of the company.

Winterkorn was angered by the fact that Porsche is now questioning Volkswagen's management strategy, a strategy that customers, dealers, the workforce, suppliers and shareholders, have faith in, he said.

"It would be a shame if this fact were not appreciated by our largest shareholder," he told the Süddeutsche Zeitung today.

Winterkorn was responding to comments made last week by Wolfgang Porsche, head of the Porsche supervisory board. Porsche told Manager magazine there is a lot of work to do at Volkswagen and that "the left hand does not know what the right hand is doing".

He criticised the amount of competition between Volkswagen brands and said that Volkswagen should "look for competition outside the company, and not within its own company".

Porsche also criticised workers for demonstrating at the company's annual general meeting in April, saying they should go back to the assembly line and work.

In today's interview Winterkorn retorted: "We don't just send our workers to the production line - we value them more than that."

Speaking separately in a local German newspaper, Volkswagen works council chief, Bernd Osterloh said: "For me it is becoming increasingly clear - the Porsche leadership obviously didn't appreciate how a global company like Volkswagen works, and they still don't."

Spiegel magazine reported that Audi managers are fearful one of Porsche's first actions when it takes control will be to axe the Audi brand. Porsche recently criticised Audi for selling the R8 sports car and the Q7 SUV at too low a price.

"Will we have to raise the prices of our models, so that Porsche can compete better?" asked one Audi manager.