New Routemaster buses will be fitted with windows after passenger complaints about stifling heat.

Journeys on Boris Johnson’s flagship buses sparked a stream complaints after passengers compared travelling in them to sitting in sauna.

In Waltham Forest multiple routes are served by the Routemaster fleet, including 15, 55, eight and 38.

Transport for London confirmed this morning the buses, worth around £350,000 each, would be upgraded at an overall cost of around £2 million.

Director of buses Mike Weston said: “We were aware of passenger concerns about the cooling system on the New Routemaster and the Mayor asked us to work with Wrights to look at possible design options to improve passenger comfort.

"We’re pleased they’ve now been able to come up with an affordable and working design to install opening windows, which we anticipate will have been installed across our entire fleet by next summer.”

Since the bus entered passenger service in 2012 there have been persistent complaints about the effectiveness of the system, with passengers complaining about uncomfortable travelling conditions.

The scorching heat was caused by faults in the vehicles’ air conditioning system and the absence of opening windows.