BERLIN (Reuters) - Volkswagen (>> Volkswagen AG) Chairman Ferdinand Piech denied he planned a second attempt to get rid of Chief Executive Martin Winterkorn after a rift between the two plunged Europe's biggest carmaker into crisis.

Piech, patriarch of the family that founded VW and a dominant figure at the firm for more than two decades, publicly withdrew his support for Winterkorn earlier this month, exposing a damaging rift at the top of the company.

Tensions appeared to ease a week ago when senior supervisory board members backed Winterkorn following a meeting with the 78-year-old Piech who could have faced calls for his own resignation had he not backed down.

"We talked things through last week and agreed to cooperate," German newspaper Bild quoted Piech as saying.

"I am not pushing for the dismissal of Martin Winterkorn," he added in comments published by the newspaper.

Earlier on Thursday, broadcaster NDR reported that Piech did not feel bound by last week's decision and was seeking support within the ruling Porsche and Piech families to replace the CEO in a vote next week by VW's 20-member supervisory board.

Hanover-based NDR said it was unclear whether Piech would push for Porsche CEO Matthias Mueller or Skoda chief Winfried Vahland as a successor to Winterkorn.

Piech's office in Salzburg declined to comment on either report while VW said there was nothing to add to an April 17 statement, which gave full support to Winterkorn.

The turmoil at the top reflects tensions between the two men that have escalated in step with the CEO's growing confidence, insiders say. It is also proving a distraction as challenges pile up and the earnings outlook darkens.

VW has for years been struggling with underperformance in the United States, declining profitability at its core autos division and failure to keep pace with rivals such as Toyota (>> Toyota Motor Corp) and BMW (>> Bayerische Motoren Werke AG) on fuel-efficient technologies.

FAMILY INFLUENCE

Shares in Volkswagen have slid about 10 percent since Piech's intial comments, wiping 10 billion euros (£7.16 billion) off the company's market value.

The Porsche and Piech families together command 50.7 percent of VW voting rights. NDR said the state of Lower Saxony, with 20 percent of voting rights, and German unions that occupy half of VW's 20 supervisory board seats, could drop their support for Winterkorn if the families were in agreement that he should go.

Both Lower Saxony and VW's works council on Thursday stuck by last week's decision and indicated support for VW's top executive, for now at least.

"The decision (to back Winterkorn) of the steering committee last Thursday was taken after thorough discussion," Lower Saxony Prime Minister Stephan Weil said in an emailed statement. "It remains the basis for the course of action."

"For us, last week's decision remains valid," works council chief Bernd Osterloh told Bild. "Internal talks will need to be held if there was need to discuss things further," said Osterloh.

Hanover-based NordLB analyst Frank Schwope does not believe Piech would find a majority on the board to force out Winterkorn before a May 5 annual shareholder meeting but said the carmaker could be locked into a protracted power struggle.

"It would be very problematic if this were to become a long drawn-out affair," Schwope said.

(Reporting by Andreas Cremer and Jan Schwartz; Editing by Thomas Atkins and Elaine Hardcastle)

By Andreas Cremer