The sex and sleaze scandal that has tarnished the reputation of Volkswagen looked like claiming another victim yesterday.

Hans-Jürgen Uhl, an influential Social Democrat member of parliament, will have to answer charges that he allowed Europe’s largest carmaker to pay for visits to prostitutes.

The Bundestag lifted parliamentary immunity for Mr Uhl on Friday at the request of the state prosecutor in Brunswick. According to press reports, the prosecutor has found at least four witnesses who would testify that Mr Uhl attended a party in a Hanover club called Sexworld.

Mr Uhl, who denied the accusations, was the head of the VW Works Council until 2002. He is a member of the IG Metall engineering union and has been at the forefront of the movement to introduce workers’ councils in Europe.

Prosecutors are investigating the possibility that VW bought the support of union representatives on the supervisory board and at workers’ council level by offering them free trips abroad and the services of escorts.

Peter Hartz, VW human resources director, will stand trial next year on charges relating to the sexual favours scandal. It is likely to be one of the most embarrassing corporate trials in Germany since former members of the Mannesmann board were put in the dock.

The revival of the VW sleaze affair could not come at a worse time for the car manufacturer.

There has been intense speculation that Porsche, VW’s largest shareholder, might soon launch a full takeover for the company, or at least boost its stake to more than 30 per cent from 27.4 per cent.

That prospect is changing the balance of power within VW, which always had a strong political component in recognition of the carmaker’s vital importance to the economy. The state of Lower Saxony owns 20.8 per cent of VW and is the second-largest shareholder.

The Prime Minister of Lower Saxony, Christian Wulff, is said to be planning a meeting with institutional investors next month to prevent a move by Porsche to seek the chairmanship of VW.

Wendelin Wiedeking, the Porsche chief executive, said that he wanted three or four supervisory board seats, rather than two.

As long as the sex scandal bubbles on, so will the wider issue of undue union influence at Volkswagen.

Porsche wants to modernise VW’s organisational structure, which has been broadly in place since the 1960s. It believes that management should be given a freer hand.

The state of Lower Saxony wants to keep jobs in the region and is ready to throw its weight behind the unions in any future showdown.

Trail of corruption claims

June 2005 Helmuth Schuster, personnel chief at Skoda, resigns after being accused of accepting bribes; Klaus-Joachim Gebauer, who allegedly paid for a prostitute on his company credit card, also resigns. Klaus Volkert, the head of Volkswagen’s work council, resigns nine months earlier than expected

July 2005 Peter Hartz, VW personnel director, resigns after being accused of allowing union leaders to take luxury trips abroad

Nov 2005 Volkswagen says an inquiry into allegations of corruption at the group will cost €5 million (£3.4 million)

Nov 2006 Prosecutors charge Peter Hartz with 44 criminal counts of breach of trust. He is accused of defrauding Volkswagen of €2.5 million