Volkswagen, the world's second-biggest automaker, admitted in September it had used sophisticated secret software to cheat exhaust emissions tests, deceiving regulators and customers about pollution from its diesel engines.

"The federal government has remained extremely timid (in the scandal) and there must be a reason for this," Dietmar Bartsch, the parliamentary group leader of the far-left Linke said. "There has been bluffing and trickery for far too long."

Anton Hofreiter, parliamentary group leader for the Greens, said that while the United States was cracking down on Volkswagen and emissions test manipulations, little was happening on this front in Germany.

"The German transport ministry has been involved in sweeping problems under the carpet," Hofreiter said.

A transport ministry report found that while no automakers other than Volkswagen had cheated emissions tests, others had made maximum use of EU exemption clauses for protecting motors.

Volkswagen last week said it booked a 16.2-billion-euro provision related to the scandal to cover potential legal costs and technical modifications.

(Reporting by Markus Wacket; Writing by Balazs Koranyi; Editing by Mark Potter)

Stocks treated in this article : SOFTWARE, PROVISION, Volkswagen AG, LEGAL, TESTS