Stephen Knight AM, who proposed the motion said: “At present the Mayor and TfL know full well that Euro 6 diesels are not actually clean, but are still planning to permit them to enter the Ultra Low Emission Zone for free after 2020 – that is simply wrong.

“The Mayor should admit past mistakes and now say that we are no longer going to put a badge of 'ultra low-emission' on a set of vehicles that are in reality nothing of the sort."

The Motion noted the events of recent weeks with Volkswagen and the defeat devices as well as the failure of recent European vehicle emissions standards to deliver the anticipated emissions reductions.

It added that TfL’s recent testing of Euro 6/VI vehicles using London drive cycles found that a number of Euro 6 passenger cars emit several times more NOx than some HGVs.

The Motion continued: “This Assembly believes that the Mayor has a duty to review his current policies and proposals in light of the emerging scientific evidence on the performance of Euro 6 vehicles under real-world driving conditions and our increasing knowledge of the adverse effects of air pollution on human health.”