Union leaders today accused London Underground of attempting to impose new "strings" over an Olympic pay deal for Tube staff after talks collapsed.
The Rail Maritime and Transport union said its executive will decide the next move over the offer of an £850 bonus for thousands of staff for working during the Games this summer.
LU said its offer would see station, maintenance, service control staff and operational managers receive up to £850 subject to attendance, customer satisfaction scores and working flexibly for defined periods to help deliver a successful transport system.
But the RMT claimed there was an attempt to "sabotage" the talks, which broke down at the conciliation service Acas after five days.
General secretary Bob Crow said: "We don't know if there has been political interference from behind the scenes but attempting to impose a whole raft of new strings on a Tube Olympics agreement at this stage smacks of an attempt from somewhere to sabotage these talks when we had said in good faith that we wanted to move the negotiations forward.
"Management wants the unlimited ability to change working patterns, locations and extend hours at the drop of a hat and to demand that staff take on safety-critical roles in unfamiliar workplaces which they aren't trained to work in.
"We would be failing both our members and the travelling public if we agreed to working practices outside of existing agreements and procedures that we know are inherently unsafe."
Howard Collins, LU's chief operating officer, said: "Over the past days we have held in-depth talks with all four Tube unions at Acas, seeking to give any clarification needed concerning our fair Olympic pay and recognition offer.
"Talks have progressed well with three unions - Unite, Aslef and TSSA - and we are optimistic that an agreement can be reached which will fairly reward staff over the London 2012 Games.
"However the RMT's leadership demanded payments to all grades of staff regardless of whether they will be asked to work flexibly during the Games and rejected temporary changes to working arrangements which would enable us to achieve a flexible workforce.
"We know our staff want to play their part in delivering a great Games for London, and we want to make sure that they are fairly rewarded for their efforts."
Mr Collins said LU will return to Acas today and urged the RMT to take part in more negotiations.
The row has flared just weeks from the London mayoral elections and could become one of the central issues of the fight between Boris Johnson and his Labour challenger Ken Livingstone.