London 2012: Union leaves Olympics Tube bonus talks
The Rail, Maritime and Transport (RMT) union says it has ended discussions with London Underground over an £850 bonus being offered to Tube workers during the Olympics.
The RMT said days of talks at the conciliation service Acas had broken down after London Underground (LU) attempted to make more demands on staff.
LU said three unions were still involved in talks.
It said it remained "optimistic".
The disagreement is around the conditions to be imposed on staff members in return for a bonus.
LU has said the payment of up to £850 would be issued in line with attendance, customer satisfaction scores and flexible working over the period of the Games.
The RMT said this effectively meant the 18,000 affected LU workers must be "prepared to work any time, any place, anywhere at the drop of a hat".
It argued that it would also put staff members in "safety-critical roles" in unfamiliar locations that they were not properly trained for, putting passengers at risk.
RMT general secretary Bob Crow said: "This dispute will now be put back in front of the RMT executive which will consider our next move."
Three unions - Unite, Aslef and the Transport Salaried Staffs' Association - are still pursuing conciliation, LU said.
Howard Collins, London Underground's chief operating officer, said: "The RMT's leadership rejected temporary changes to working arrangements which would enable us to achieve a flexible workforce."
He said he hoped the RMT would rejoin talks on Thursday to resolve the issue.