“We want to completely rule out animal experiments for the future. This is to make sure it doesn't happen again,” Thomas Steg, VW’s public relations chief, told Bild newspaper on Tuesday.
“What happened should never have happened, I regret it very much,” Steg added.
VW also on Tuesday vowed internal “consequences” over the experiments.
VW chief executive Matthias Mueller labelled the 2014 animal testing “wrong … unethical and repulsive” and promised the company would bear “all necessary consequences”, reported Spiegel Online.
The scandal follows VW's admission in 2015 that it had manipulated 11 million diesel cars worldwide, equipping them with cheating software to make them seem less polluting than they were.
According to the New York Times, US researchers in 2014 locked 10 monkeys into airtight chambers and made them breathe in diesel exhaust from a VW Beetle while the animals were watching TV cartoons.
Separately, it emerged that a research group funded by VW, Mercedes-Benz parent Daimler and BMW had ordered a study in Germany measuring the effects of inhaling nitrogen dioxide on 25 human volunteers.
The disclosures sparked widespread outrage, led by Chancellor Angela Merkel who strongly condemned the latest controversy to engulf the nation's powerful auto industry.
“These tests on monkeys or even humans are in no way ethically justified,” said Merkel's spokesman Steffen Seibert on Monday. “The indignation felt by many people is completely understandable.”
Steg admitted to Bild that he had been informed in advance of the US monkey experiment but insisted he prevented a plan to carry these tests out on humans.
As for the German tests conducted in an institute in Aachen in 2013 and 2014, Steg said the volunteers had been exposed to “much lower levels than those found in many workplaces” and that no-one suffered any harm.
All three German carmakers scrambled to distance themselves from the research body in question — the now defunct European Research Group on Environment and Health in the Transport Sector (EUGT) — and promised to launch internal investigations.
The German government has called a special meeting with the affected car companies to ask them to explain themselves.
Although it was the EUGT that commissioned both tests, the organisation itself was financed by the trio of car giants hoping its research would defend diesel's green reputation.
The car companies decided in late 2016 to dissolve the EUGT, which shut its doors last year.
Amid the controversy, Berlin's Tageszeitung daily said that “while these experiments are doubtless scandalous, the bigger scandal is the experiment the car industry has been conducting on the wider population for decades”.
“While the monkeys and human volunteers only had to inhale exhaust fumes for a few hours, people with the misfortune to walk along arterial roads have been breathing in levels of nitrogen oxide far higher than EU limits for years.”
In Brussels, the EU Commission on Tuesday summoned Germany and eight other EU countries to explain how they plan to lower toxic emissions to meet the bloc's air quality standards if they want to avoid action before the European Court of Justice.