The frequency of the 31 service was reduced recently, from every 12 to every 15 minutes. Lothian Buses said at the time this was to make the service more reliable. This has not been the case.
Local Lib Dem councillor Robert Aldridge said, "We know this is a difficult period for bus services, with both recruitment and retention being a real challenge, but Lothian has a responsibility to provide a service to the city.
"The 31 is the only service that goes into the main body of East Craigs - it's vital.
"Ed Thornley and I will be writing to Lothian to express the frustration and disappointment felt by local residents that their only bus service is continuing to let them down, and to urge them to improve the 31."