Bus drivers at Metroline in north London were due to hold a consultative strike ballot across all its garages on Friday of this week.
The ballot is over a series of issues relating to the treatment of workers at the company.
Unite union members are concerned about the company’s new drugs and alcohol policy.
This includes fears about the broadness of the criteria under which managers can send drivers for testing.
The ballot also relates to concerns over increases in canteen prices, a rise in disciplinaries and changes to some overtime arrangements.