It's claimed that staff based in Stratford are paid less than "their brothers and sisters elsewhere on the Underground". The pay gap is said to have grown to thousands of pounds.
However, on Wednesday a new proposal was put to the table for the RMT to consider.
Bob Crow the RMT leader said "Despite lengthy talks aimed at reaching an agreement that ensures that Stratford Market depot fleet staff get the same wages as their brothers and sisters elsewhere on the Underground, Alstom have dug their heels in and left us no option but to take decisive action to break the deadlock.."
A TfL spokesperson told the Press Association: "This is a matter for Tube Lines, its contractors and the RMT and we urge them to resolve the matter quickly without any disruption to Londoners."
It's hoped that a decision will be made by Monday.
Update - Jan 27th 2010 - These have been suspended as a new pay offer is now being considered.