Porsche’s slowly tightening grip on Volkswagen is causing some ruffled feathers among upper management. Porsche is on the verge of increasing its stake beyond 50% in Europe’s largest carmaker and is expected to flex its muscles by controlling everything from product development to labor negotiations. However, the CEO of VW, Martin Winterkorn, is fighting back and has said in an interview that he will resign his post if Porsche interferes with his company’s operations.

One of the biggest fears for Volkswagen is that Porsche may limit Audi’s model range to prevent competition with its own range of sports cars, SUVs and (soon to be available) sedan. According to a German report in Der Spiegel, one Audi insider has said that Porsche is already criticizing the company for its R8 sports car and Q7 SUV. In the future, the insider claims, Porsche may limit the price bracket of Audi vehicles to ensure they don’t compete, however this would damage Audi’s ability to compete with BMW and Mercedes, who are both pushing their brands in to higher – and lower – market segments.

Previously Porsche has also stated that ‘fun projects’ such as the Bugatti Veyron would need to be canceled if they were not capable of making a profit. Both Lamborghini and Bentley are currently profitable so they should be safe, however a slide in sales could potentially mean VW would be forced to sell them off at the behest of its largest shareholder.

Winterkorn has also stated he’s worried about the welfare of Volkswagen workers. Porsche is known to push efficiency at all costs, however Winterkorn said the workers must be treated with “appreciation.”

The rivalry between VW and Porsche’s management teams has taken some strange turns in recent times with Volkswagen being accused of spying on Porsche CEO Wendelin Wiedeking using a baby monitor.