Transport for London has admitted that the evening peak service on bus route C10 is not reliable enough.
Route C10 links Victoria with Canada Water via Elephant & Castle and Bermondsey.
A new timetable was introduced on the route this week increasing the westbound morning peak hour frequency from every 10 minutes to every eight minutes.
Labour London Assembly member Val Shawcross tabled a question to the Mayor asking him to improve the evening rush hour service on the route.
She told Boris Johnson: "Poor performance on the C10 bus route has been a subject of much discussion on the SE1 website forum recently, including an incident whereby frustrated passengers refused to get off a C10 which had terminated early at Elephant & Castle in the evening rush hour, instead of continuing through Rotherhithe.
"I appreciate that TfL are making efforts to improve the service in the morning but it seems a further more large scale review is required. Please ask TfL to instigate this."
Mr Johnson's reply was published on Monday: "Although route C10 generally operates to a good standard, TfL is aware that the reliability in the evening peak should improve.
"It is working with the operator to consider how best to do this."
Local Labour and Lib Dem politicians have both claimed credit for lobbying Transport for London for the extra morning peak services on the C10.
Simon Hughes MP said: "I am delighted to see that all the hard work and campaigning which Caroline Pidgeon, Southwark Liberal Democrat councillors and I have done is paying off and that Transport for London has now agreed to run more buses on the C10 route.
"As the economy recovers, it is vital that we continue to build up our local transport infrastructure for local residents and to make sure that Bermondsey and Southwark are seen as great places to locate or start a business."