Complaints about sweltering conditions on Boris Johnson's new Routemaster-style buses soared this summer, new figures released to Politics.co.uk have revealed.
The buses currently only operate on a handful of routes across the capital.
However, faulty air-conditioning and an absence of openable-windows have made the buses notorious for oppressively hot conditions on the top decks.
Many passengers have taken to social media to complain about the heat and accompanying odours on the buses, with some even posting photos of eye-watering thermometer readings.
Even Johnson has joked about the "Bikram-yoga style" conditions on the buses.
However, Transport for London have consistently denied any problem with the buses, with commissioner Peter Hendy describing the complaints as an "urban myth".
In order to test this out, Politics.co.uk asked for details of all passenger complaints they had received about the buses.
TfL initially refused, saying it would be too expensive to count them.
However, a further request has revealed widespread passenger discomfort.
According to the figures released under freedom of information, there were more than 150 official complaints logged with TfL by passengers in June and July this year.
In the last two weeks of July alone, there were 86 complaints with up to 15 complaints registered with TfL a day.
Many more complaints were registered via social media, but have not been counted in these figures.
So hot on this bus. I really don't understand why this stupid new 148 doesn't have windows.— Libra? (@Akiema_MsYellow) July 18, 2014
@TfLTrafficNews hi I just to complain about the new route master bus like 148 and 390 super hot no window no air con, very suffocating...— lyn.b .nacorda (@lynxinlondon) July 18, 2014
Every "new Routemaster" I've seen today has had a conductor hanging out the back in a bid to cool down. Not an option for passengers.— Primly Stable (@PrimlyStable) July 18, 2014
The mayor's opponents today urged Johnson to get to grips with the problem.
"The Boris bus has been promoted as the future for London’s transport, but the reality will be years of sweltering passengers as London’s summers get warmer," Green party London Assembly member Darren Johnson said.
"Last year, the Mayor said the air cooling system had technical problems but they would be fixed.
"This year, they say that everything is fixed but the passengers are still complaining about over-heating. The problem is the design of the bus, not the air cooling system. I have no doubt that the next Mayor will cancel the whole project, but London will still be stuck with 600 buses, on our streets for the next 14 years, where you can’t open the windows."
A spokesperson for TfL blamed "unseasonably warm" summer weather for the unpleasant conditions experienced by passengers..
"We acknowledge passengers have suffered some discomfort during exceptionally hot days," they told Politics.co.uk.
"However, during this time, the air-cooling system on New Routemasters was providing cooler than ambient air, and monitoring of the upper decks of buses in service indicated performance was at least as good as other double deck buses in the fleet," they added.
Politics.co.uk last month asked for details of the independent checks they claim to have made on temperatures on the buses.
They have so far failed to release them.
TfL also said they had no plans to install openable windows on the buses.
"The system on [New Routemasters] is designed to work without windows being open – just as with air conditioning systems in offices and cars, having opening windows would reduce the efficiency of the system."
The spokesperson said TfL have no plans to increase air conditioning, due to environmental considerations.
"We must strike a balance between providing reasonable comfort in summer conditions and minimising exhaust emissions from the bus fleet. Installing full air conditioning systems on buses would dramatically increase harmful exhaust emissions," they added.
Earlier this year Politics.co.uk revealed that the signature 'open rear platforms' on the buses are being routinely closed on many of the buses with some being shut off permanently due to health and safety fears.