Bus routes 507 and 521 will become the first in the centre of the city to be run exclusively by all-electric vehicles by the end of the year.

Mayor of London Sadiq Khan and Transport for London (TfL) said this fleet of 51 electric buses will take the city's total to 73 - more than any other country in Europe.

It is the first step towards a plan to make all 300 central London single-decker buses zero emission vehicles.

The new buses will be the first to include screens showing the next five stops and how the Tube and Overground is running, as well as 12 seats with USB sockets to enable passengers to charge their mobiles.

The single-deck buses will be made in Britain by Chinese company BYD and Scottish manufacturer Alexander Dennis.

Mr Khan said: "It's vital that we act now to clean up our capital's toxic air and do everything we can to help prevent the thousands of deaths it causes each year.

"I've set out a comprehensive plan to improve our air, and the transformation of London's bus fleet will play a key role in making our transport cleaner and healthier.

"These first two electric bus routes right through the heart of London are another step towards the end of conventional diesel buses on our roads.

"This will deliver extensive air quality benefits and position us as a true world leader in adopting ultra-low-emission vehicle technology."

London currently has around 2,000 hybrid electric buses, representing roughly 20 per cent of the fleet.