Ouzký denied that Gerhard had written the bill. "The PowerPoint table that I used to formulate the amendment had originally been drafted by Porsche so it has their signature on it," he said in a statement.
"However, I only used that as a template to fill in the compromise proposals based on a middle way between all of the amendments that I had received."
Porsche also denied that they had attempted to influence the bill. They told the news website Euractiv that Gerhard had been writing in his capacity as the chairman of the noise-pollution group at the International Organisation of Motor Vehicle Manufacturers (OICA). They said that Ouzký's statement that the bill was "drafted" by Porsche was "wrong".
Ouzký's bill was defeated in the European parliament by a single vote in December 2012.
Müller's predecessor as VW chief, Martin Winterkorn, resigned on Wednesday after the German car giant was found to have used software to manipulate the results of its diesel emissions tests. As many as 11 million cars are believed to have been affected.
A spokesperson told Business Insider this week that Porsche has its own testing regime and its cars' results had not been manipulated.
Nico Muzi, a spokesman for Transport and Environment, told BuzzFeed News: "The issue here is not confidence in an individual's ability as a manager. What's crucial is that Europe should have robust testing and proper enforcement as the US does, so that those who cheat pay for it."
BuzzFeed News has contacted Porsche for a response.