European lawmakers approved on Thursday a wide-ranging probe into the Volkswagen emissions scandal and allegations that EU regulators turned a blind eye to suspicious pollution testing of diesel cars.

"After the revelations putting the role of the European Commission into question, it is necessary that the European Parliament provide some transparency to the issue," said Greens MEP Karima Delli, after parliamentary group leaders approved the investigation.

The European Commission, the EU's regulatory arm, has drawn fierce criticism since the scandal erupted in September that it ignored evidence that Volkswagen was using so-called defeat devices to pass pollution tests.

Defeat devices are sophisticated software fitted into diesel engines to skew the results of tests for nitrogen oxide emissions.

It was the major discrepencies in test results, enabled by the devices, that prompted authorities in the US to confront Germany's Volkswagen, sparking the scandal that has rocked the auto industry.

The commission firmly denied the accusations that it failed in its regulatory duties and said it would cooperate fully with the inquiry.

"The Commission is more than ready to work with the European Parliament's Committee of Enquiry," a spokesman from the commission said in an email sent to AFP.

The commission also added that while it is responsible for setting pollution limits on cars and defining testing procedures, it has no control over enforcement, which is left to national authorities.

"The policing in the area is the responsibility of the appropriate national enforcement authorities," the commission said, adding that defeat devices were banned in the EU.

The European Parliament said the inquiry committee would release an initial report within 6-months of the probe's launch, with a full report after one year.