By William Boston 

BERLIN-- Martin Winterkorn, Volkswagen AG's former chief executive, on Thursday denied any personal knowledge of the German car maker's diesel-emissions cheating in his first major public appearance since the scandal broke in September 2015.

Mr. Winterkorn was forced to resign just days after U.S. environmental authorities disclosed that the company had rigged diesel engines to cheat on emissions tests. The disclosure led to civil and criminal litigation against the company, which has pleaded guilty to federal charges including conspiracy to defraud the U.S. government and U.S. consumers.

Flanked by two lawyers, Mr. Winterkorn sat calmly at the witness table facing members of a German parliamentary committee, who peppered him with questions about his knowledge of the use of cheating software. He denied any personal responsibility, but declined to answer questions that became too specific, citing ongoing criminal investigations in the U.S. and Germany.

"Of course I ask myself if I missed signals or misread them," he said, adding that he was still "searching for satisfactory answers" as to how the decision to cheat was made and why.

He described his profession as "engineer" and acknowledged his love of detail, saying it was his "personal brand," which is why "everyone is saying 'Winterkorn must have known everything.' But that's not the case."

Mr. Winterkorn's fall from power in the wake of the scandal was swift and deep. In his testimony in German parliament, it became clear that he previously had frequent contact with Chancellor Angela Merkel and other top politicians who sought his economic counsel.

Mr. Winterkorn testified that he first learned that the emissions problems in the U.S. were the result of the use of illegal software, a so-called defeat device, in September 2015, just as the scandal broke. He said he was informed at 6 p.m. on Friday, Sept. 18, that the U.S. would charge Volkswagen with emissions violations, minutes before the Environmental Protection Agency published its official notice of violation.

The following day, he said, key members of the company's management board held a telephone conference to discuss "what was going on in the U.S." On Sunday, Sept. 19, "we met in the big group" at the company's headquarters in Wolfsburg. The supervisory board met the following day, Sept. 20.

"During our meeting on the weekend it became clear that it wasn't just a U.S. problem," he said, adding that it wasn't until Tuesday, Sept. 21, that he became aware of the full scale of the diesel affair, that nearly 11 million vehicles world-wide were affected.

On that Tuesday, Mr. Winterkorn spoke on the phone with Ms. Merkel and told her "we have problems not only in the U.S. but also in Germany."

Mr. Winterkorn said he tried to explain to Ms. Merkel how the company could have resolved the issue. But he soon discovered that it would be someone else's responsibility to fix the problem. Mr. Winterkorn resigned under pressure on Sept. 23.

"As CEO I took political responsibility," he told the lawmakers, repeatedly denying personal involvement in or knowledge of the fraud. "I am a realist and have to accept that my name will be closely associated with the diesel affair."

Write to William Boston at william.boston@wsj.com

(END) Dow Jones Newswires

January 19, 2017 09:08 ET (14:08 GMT)