HAMBURG/BERLIN (Reuters) - Ex-Volkswagen VOWG_p.DE Chairman Ferdinand Piech, who resigned after a showdown with former chief executive Martin Winterkorn, has refused to testify to German lawmakers investigating a possible government's role in the VW emissions scandal, according to his lawyer.

Ferdinand Piech, chairman of the supervisory board of German carmaker Volkswagen, arrives at the annual shareholders meeting in Hanover in this April 25, 2013 file photo. REUTERS/Fabian Bimmer/Files

Piech, also VW’s former CEO who spearheaded the carmaker’s global expansion, gave testimony to lawyers of U.S. law firm Jones Day last April and to German prosecutors in Braunschweig near VW’s Wolfsburg headquarters in December, his lawyer said.

“These comments were solely directed at the inquirers of Jones Day and the prosecutors respectively. They were not directed at the public media,” Piech’s Hamburg-based lawyer, Gerhard Strate, said in an emailed statement.

He said Piech has no intention “to comment in public on what is being circulated as the alleged content of the questioning”.

A German media report earlier this week said Piech had informed top directors at VW about potential cheating with diesel emissions tests in the United States six months before the scandal became public in September 2015.

Piech has not commented on the report by Bild am Sonntag.

The unsourced report said Piech raised the issue with Winterkorn and subsequently informed members of the supervisory board’s steering committee in March 2015 - a month before Piech was ousted as chairman.

A person familiar with the matter told Reuters on Sunday that Piech had raised the issue of excess diesel emissions of VW cars in the United States with Winterkorn in March 2015.

The former CEO then replied to Piech that a recall of affected vehicles was already underway and that the problem would be resolved, the person said, adding that Winterkorn last year had given the same account to Jones Day.

Winterkorn’s lawyer has said his client would not be commenting until he had been granted access to files held by Braunschweig prosecutors.

VW has said it might take legal action against Piech over his reported assertions. The supervisory board’s labor representatives have since denied the reported allegations, as did Stephan Weil, a member of the steering committee and prime minister of Lower Saxony state, VW’s No. 2 stakeholder.

Left Party lawmaker Herbert Behrens, who chairs the German parliamentary committee tasked with investigating the emissions irregularities, said earlier this week that the latest escalation required a Piech testimony.

Behrens didn’t return calls seeking comment while fellow committee member Oliver Krischer, a Green Party lawmaker, criticized the refusal to testify.

“This of course damages the (VW) brand and the entire German auto industry if those involved, even if they no longer belong to the company, do not manage to draw a line and clear the air,” Krischer told broadcasting network Deutschlandfunk.

The eight-member cross-party committee will question Weil and Transport Minister Alexander Dobrindt over the scandal on Thursday.

The panel was set up last April to clarify whether Germany’s federal government and regulators were involved in VW’s emissions manipulations or failed to contribute towards their disclosure.

Last month it questioned Winterkorn, who denied early knowledge of the cheating.