September 25, 2015 - 8:54 am ET  FRANKFURT (Reuters) -- Daimler reiterated today that it has not used defeat devices to manipulate its vehicles during emissions tests. The denial follows allegations by lobby group Deutsche Umwelthilfe (DUH) that it had rigged emissions data for its vehicles. The DUH said on Thursday that tests had shown vehicles made by German carmakers including Daimler significantly exceeded limits on nitrogen oxide emissions. "We sharply deny the allegation that we manipulated our cars during emissions tests. We never did and do not now use a defeat device," Daimler said in a statement. It said it was unaware of any data showing its vehicles breached legal limits and said it was willing to have any of its vehicles tested. Daimler's statement comes after U.S. regulators said a week ago that fellow carmaker Volkswagen Group had admitted to programming diesel cars to detect when they were being tested and alter the running of their engines to conceal their true emissions.