Bosch GmbH supplied the exhaust management software for Volkswagen's EA189 2.0 litre turbo diesel engine, which is now the focus of investigations after American authorities discovered it was specifically designed to cheat emissions tests.
And according to unnamed sources within Bosch, the parts supplier was aware of Volkswagen's intentions to use the now-infamous "defeat device" eight years ago, and had warned Volkswagen that such an act would be illegal.
The EA189 engine (pictured) was fitted to some 11 million cars sold worldwide across the VW group, including Volkswagen, Audi, Skoda and Seat.
Published by German paper Bild am Sonntag, the report claims Bosch explicitly stated in a letter to Volkswagen that the use of its software to circumvent emissions regulations was against the law, and that it would supply the software only on the basis that it was for test purposes.
German newspaper Frankfurter Allgemeine Sonntagszeitung also reported that a Volkswagen engineer raised concerns about the company's deceptive engine management systems in 2011.
Both the warnings of Bosch and that un-named engineer were reportedly ignored.
The EA189 crisis, dubbed "Dieselgate" continues to affect Volkswagen, whose former CEO Martin Winterkorn resigned last week as its share price plummeted.
Winterkorn's successor Matthias Muller was appointed on Friday and VW's stock price has stabilised somewhat, though with several investigations into Volkswagen diesels still underway in Europe and across the globe the full impact of the scandal has yet to become apparent.