The Mayor of London has written to Volkswagen imploring the car giant to "fully compensate" the capital's residents affected by the emissions scandal.
Sadiq Khan has called on the German firm - known as VW - to reimburse Transport for London (TFL) some £2.5 million in lost Congestion Charge revenue from vehicles which were unknown to be contributing to the capital's pollution.
It has been more than a year since the Environmental Protection Agency in the US said 482,000 Volkswagen-built cars were fitted with sophisticated software which detected when the vehicles were undergoing official emissions testing and switched the engines to a cleaner mode.
The car giant - responsible for models such as the Polo and Golf - later admitted that 11 million vehicles worldwide were fitted with the software. It set aside 6.5 billion euro (£4.7 billion) to deal with the cost of the scandal.
In his letter, Mr Khan said: "There is no excuse for the utter lack of action VW has taken in London since the 'dieselgate' scandal came to light.
"I want to see a proper commitment from them to fully compensate the thousands of Londoners who bought VW cars in good faith, but whose diesel engines are now contributing to London's killer air.
"I also urge them to reimburse TfL the £2.5 million lost in Congestion Charge revenue, which I will use to fund a new schools air quality programme that will reduce the exposure and raise the awareness of schoolchildren in London attending schools in the most polluted areas."
It is estimated the equivalent of up to 9,400 deaths occur each year in London due to illnesses caused by long-term exposure to air pollution, with 448 London schools in areas exceeding legal air quality levels
Of the 500,000 VW vehicles registered to addresses in London, it is estimated 80,000 are model 2009-2015 – those in which suspect devices were used.
The mayor has also asked VW for a progress update on their commitment to re-programme the defeat devices in affected vehicles and the expected completion date.
Vickie Sheriff, director of campaigns and communications at consumer group Which?, said: "Volkswagen's customers in the UK cannot understand why US consumers are being paid compensation when there is nothing on the table for the 1.2 million owners affected in the UK.
"The Government must urgently get to grips with this matter and ministers must launch their investigation now.
"VW simply cannot be let off the hook any longer."