While hybrids such as the Toyota Prius have become synonymous with the ride-hailing service, today just under half of its London UberX drivers have an electrified vehicle. The firm said that must rise to 100 percent by 2020.
Diesel-powered cars on the app's other services, such as UberXL for larger cars, will also be banned from 2020 in the capital.
For other U.K. cities blighted by dirty air, where fewer UberX cars are electrified already, the 100-percent hybrid and electric deadline is 2022.
In the longer term, the U.S. company said that by 2025 all of its cars in London must be fully electric or a plug-in hybrid, on which the battery typically lasts about 40 miles before switching to petrol.
Jaguar Land Rover followed Volvo last week by promising to no longer launch new models that are not electrified to some degree, though it will continue selling existing petrol and diesel models.
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