Porsche, the luxury sports carmaker, could raise its stake in Volkswagen to close to 30% to cement its control over Europe's biggest auto-manufacturer after the enforced resignation of Bernd Pischetsrieder as chief executive, sources said yesterday.

Mr Pischetsrieder quit late on Tuesday after a management committee headed by the VW chairman, Ferdinand Piech, unanimously delivered a vote of no confidence.

VW refused to explain the shock departure but it followed a protracted power struggle between the two men. Mr Piech, a scion of the Porsche family, had the full backing of the powerful IG Metall union over the scale of proposed restructuring. VW is cutting 20,000 jobs in Germany.

Analysts also pointed to sharp dissension within the board over Mr Pischetsrieder's role in pursuing a three-way tie-up between Swedish and German truck-makers Scania and MAN.

He is to be succeeded on January 1 by Martin Winterkorn, head of VW's highly profitable premium cars division, Audi.

Analysts said the decision to get rid of Mr Pischetsrieder cast doubt over VW's restructuring plans, designed to deliver €5.1bn (£2.3bn) pre-tax profits by 2008, and other senior management posts.

IG Metall arranged a deal raising VW's working week in its six German plants for no extra pay but is known to have scuppered earlier plans to sell off or close component plants.

Investors are worried that the union has regained a powerful hold over decision-making at VW. But some analysts argue that Mr Pischetsrieder was removed because of his lack of ruthlessness in executing VW's recovery programme.