The RAC has called for more stringent, representative lab tests in the wake of the Volkswagen emissions-rigging scandal.
David Bizley, chief engineer, says such tests need to better reflect real-life motoring. His plea comes as Labour called on the Government to reveal when they became initially aware of the scandal.
Lilian Greenwood, shadow transport secretary for Labour, described the Department of Transport's (DfT) response as "unacceptable". Patrick McLoughlin the Transport Secretary said on Monday that every diesel vehicle will need to get re-tested in Britain.
These latest moves come in the week that VW announced it had appointed Matthias Mueller to take over from Martin Winterkorn, who has resigned , as its chief executive.
It was later announced that Mr Winterkorn faces criminal proceedings over the scandal. An investigation has been opened which will concentrate on the purported fraud as well as trying to establish who the responsible parties are.
David Bizley said: "In light of the emissions tests revelations, car buyers need to be given absolute confidence in the emissions and fuel economy performance of their new vehicles.
"We believe this is best achieved through a more stringent laboratory test that is more representative of 'real world' driving.
"There has been much debate about the nature of tests but while on-road tests are often thought to be the answer, these would not be sufficiently repeatable or reproducible to ensure reliable results.
"A laboratory test has to be the main element of any approval process, but the test method needs to be more representative of real-world driving, with the caveat, of course, that it will never completely mirror a car being driven on a real road by different drivers.
"The new worldwide laboratory test - due to be implemented in Europe in 2017 - aims to address this by incorporating a wider range of vehicle operating conditions with four test modes of low, medium, high and extra high - or in real-world driving terms: urban, rural, motorway and autobahn.
"This is a positive step as vehicles are known to emit more nitrogen oxides at higher speeds, and under heavier loads, which current tests do not take sufficient account of.
"It is also important to note that this may lead to vehicles being found to emit greater quantities of nitrogen oxides than current test results indicate.
"What is needed to ensure production vehicles meet the standards is a robust protocol involving not just a laboratory test but also an on-road 'conformity' test which cannot easily be identified by the vehicle's software.
"This way vehicles found to have drastically differing results would be automatically identified and investigated.
"The combination of a lab test and an on-road test would also go a long way towards allaying motorists' long-held concerns about manufacturer-claimed mpg figures being so much better than what they actually see on their dashboard computers while driving.
"This discrepancy is purely another aspect of the emissions problem as they are generated from the same test data.
"It is therefore no surprise real-world mpg figures are lower than those generated under laboratory test conditions."
Ms Greenwood called it "unacceptable" that ministers have delayed taking action until now. This is a year after the International Council on Clean Transportation (ICCT) first warned that highly dangerous nitrogen oxide discharge rates went beyond the US.
Greenpeace environmental campaigners have written to ministers, asking if they knew anything about the emission test rigging prior to this month. John Sauven, its executive director in Britain, says that several people wish to know if UK ministers put pollutants' profits before their citizens' health.
The DfT says that the British Government is among the prime European movers in launching emissions testing upgrades.
Copyright Press Association 2015