The world's first purpose-built pure-electric double-decker bus is to hit the streets of London in October.

Passengers on route 16, between Cricklewood and Victoria station, will be part of a new trial to test the latest technology aimed at producing low-emission buses.

London Mayor Boris Johnson, who made the announcement at a Clean Bus Summit at City Hall, said: "The iconic red double-decker bus is about to become greener than ever."

He also announced that the 312 single-decker bus route, between Norwood and South Croydon, will become London's first pure-electric route later this year.

No fixed date has been set for when the trial is to end.

Bus manufacturers have been working on ways to make the buses cheaper to buy and operate in the bus fleet.

London is one of 24 cities which have pledged to roll out over 40,000 ultra-low emission buses by 2020.

London's transport commissioner Sir Peter Hendy said: "The introduction of new electric buses and further developments like induction charging at termini for hybrid bus batteries will significantly improve air quality and provide our passengers with quieter and smoother journeys later this year."

Bus manufacturers and transport industry representatives were among the guests who attended the summit.