Tube drivers at a north London depot are planning two 24-hour strikes on the London Underground (LU) over a long-running row with a manager.
Drivers could cause chaos for commuters if a strike goes ahead on Christmas Eve
About 150 members of the drivers' union Aslef on the Jubilee Line will walk out on 3 December and Christmas Eve.
District and Piccadilly line drivers are also being balloted on action as part of a row over working conditions and a union member's demotion.
The results will be announced later this week.
LU is trying to set up fresh talks with Aslef to avert industrial action.
A spokesman for LU said: "Strike action will not resolve these disputes.
"We will be looking to speak to Aslef representatives soon to find a way forward."