East London Bus Group is threatening to slash wages for all workers. Supervisors face a pay cut of up to £5,000 a year.
Bus drivers in the Unite union are holding a union meeting this week to plan a campaign.
Drivers at Arriva North in London have shown what can be won. They got a £750 lump sum for their 2009 settlement and a 2 percent pay rise for 2010.
Attacks on conditions were originally attached to the deal, but management dropped these after the threat of action.