In the programme, aired yesterday, the people carrier was said to have emited two and a half times more nitrogen oxide than is allowed in a lab test.

However, in response, Vauxhall said it has clearly stated that its vehicles do not have any feature that detects that a vehicle is undergoing an emissions test, including any feature that would respond to wheels turning.

It added: “We suspect that the vehicle tested (Zafira 1.6 diesel) was not performing correctly and/or the test execution was not correctly set up.  In order that Panorama did not potentially draw the wrong conclusions from their testing we requested full test reports and data from the testing including how the vehicle and test was set up, the technical state of the vehicle and details of the pre-conditioning of the vehicle which is necessary to achieve a stabilised condition for the test.

“Panorama has refused to share information on the technical accuracy of the test prior to the broadcast.

“When DUH tested the Zafira in Germany they were not willing to share their results before they went public.  We subsequently concluded that the campaign contained misleading elements. In response to the incorrect accusations of DUH we ran a full series of tests. Those tests proved that the Zafira 1.6 meets all the legal emission limits both in 2WD and 4WD roller testing. Those 4WD tests were conducted under the supervision of the TUV agency and officially protocolled.”

The Zafira has already been in the headlines in the last month due to an issue with customer reports of fires.