Robert Hogg, chairman of the Midlothian Federation of Community Council and Mayfield and Easthouses Community Council, has experienced the boiling buses himself and heard the concerns of others.
Lothian Buses denied there is an issue with its heating or cooling systems on its buses.
Mr Hogg claims fans on the buses are blowing out hot air, as temperatures have soared in recent months.
He said: “Lothian Buses claim they have some of the most modern buses in Britain but there is a fault with their fan heaters on the buses meaning the drivers can’t put them off. It’s been like that for years now but it has been worse during the last few weeks with buses packed during the school holidays and the Edinburgh Festival.
“Passengers young and old have been suffering during the recent heatwave. But there is nothing drivers can do to turn them off. Apparently it’s fixed by the engineers at the depot.
“It’s on all the Lothian Buses. Not just certain services. It’s unbearable. It’s the older folks and mothers with bairns I sympathise with the most. It must be horrendous for them.
“Everytime I have been on a bus recently people are speaking about it. I have asked the driver to turn the heating off but they can’t do anything about it. It’s a well known problem. I have heard lots of people talking about it. Something needs to be done.
“Somebody could pass out. Some drivers have been forced to stop their buses due to passengers being so hot.
“It’s hot enough outside so the last thing you want on a bus is heat coming out from underneath the seats.”
A spokeswoman for Lothian Buses said: “Our buses regulate the interior saloon temperature by means of a thermostat which then feeds directly to either the heating or cooling system controls as appropriate like in a house. Drivers can then control the heating as required. If customers experience discomfort with heating they should speak to the driver to ask them if it is possible for the temperature to be adjusted accordingly.
“In recent weeks we have experienced unusually long spells of extremely hot weather which has had an impact on the overall temperatures inside our vehicles coupled with heavy loadings during the summer, which in itself increase the ambient temperature. Additionally the regular opening of doors also draws warm air from outside.”