The @jubileeline is now operating with minor delays due to an earlier signal failure at Waterloo. Trains and platforms may still be busy
The problems come just one day after news that drivers on the Jubilee line are to be balloted for industrial action in a row over working conditions and allegations of bullying.
Members of the Rail Maritime and Transport union on the Jubilee line will vote in the coming weeks on whether to launch a campaign of industrial action.
RMT general secretary Bob Crow said: "Our members will not sit back and allow the misuse of procedures to bully and intimidate our members, and they are are sick of the gradual decline in working conditions."
John Doyle, Jubilee Line general manager for London Underground, said: "The unions have informed us that they are in dispute with us over what they perceive as a breakdown in industrial relations.
"We are keen to understand their concerns and so will be meeting with the union later this week to discuss these issues in greater detail."
RMT: Jubilee line pretty much closed due to signal failure affecting three quarters of a million passengers. @itvlondon
RMT's Bob Crow: Breakdown once again raises serious questions about the automated operating system on that service. @itvlondon