Almost two thirds of staff see "no improvement" in Volkswagen's (VW) corporate culture almost two and a half years after the diesel emissions fraud was revealed, works council chief Bernd Osterloh said on Thursday, citing results of a labour survey of more than 51,000 workers carried out in December at German plants.

The attempt by Europe's largest automaker to become more transparent and improve troubleshooting is seen by investors as a key part of VW's ability to regain trust and avoid any future scandals.

There is also the potential for VW employee discontent with management to prompt labour leaders to adopt a tougher stance in dealings with top executives.

"Culture change for us remains a permanent work site," Osterloh said on Thursday in comments released on VW's internal communications network.

Group human resources boss Karlheinz Blessing, commissioned to lead the change in culture at Wolfsburg-based VW, said the transformation needs more broadbased support to succeed.

"We have been saying all along that a culture change cannot be implemented over the short term and takes time and is also not the work of an individual or of individual participants," he said in a separate interview published internally at VW.

"All stakeholders are urged to bring about this culture change."

Separately, Osterloh, who is seeking re-election as works council chairman next month, said that workers were critical of internal communication by management and expressed concerns about job safety and retirement conditions.

Given the continued negative news flow about VW with the latest revelations of VW-sponsored diesel fume tests involving monkeys and humans and prosecutors' raids on luxury brand Audi, it's no surprise that sentiment among staff is declining, Blessing said.

"With the negative headlines that keep surprising us, it would be remarkable if sentiment was not affected," he said. "We can only apologise to staff for what they have to put up with, even though we are not the originator of these headlines."

(Reporting by Andreas Cremer and Jan Schwartz; Editing by David Goodman)