The head of VW cars in the UK has apologised "unreservedly" for "significantly" letting down its customers in the diesel emissions scandal.
It comes days after the American boss of VW made a 'sincere apology' over the scandal which has affected more than 11 million cars worldwide.
Volkswagen has disclosed to US regulators that there is additional suspect software in its 2016 diesel models that would potentially help their exhaust systems run cleaner during government tests.
The manufacturer told Associated Press that the "auxiliary emissions control device" at issue operates differently from the "defeat" device software included in the company's 2009 to 2015 models disclosed last month.
The newly revealed software makes a pollution control catalyst heat up faster, improving performance of the device that separates smog-causing nitrogen oxide into harmless nitrogen and oxygen gases.
VW spokeswoman Jeannine Ginivan said: "Volkswagen has disclosed, in the application process for the model year 2016 2.0 TDI models, an auxiliary emissions control device. This has the function of a warmup strategy which is subject to approval by the agencies.
"The agencies are currently evaluating this and Volkswagen is submitting additional information."
Volvo withdrew an app comparing cars' emissions in 2011, after being told by that the data "could not be taken seriously".
Volkswagen's US boss has admitted he was told in spring last year of the emissions cheating affecting millions of the company's vehicles.
Volkswagen could start recalling cars containing emissions cheating software in January, according to the firm's new chief executive.