Tube workers’ unions have declared an official dispute with London Underground.
Bosses are imposing new rosters on staff in the run-up to the start of all three night Tube lines in September.
This would mean drivers will have to work an unlimited number of weekend and night shifts for no extra pay.
For other staff it will lock them into a regime of unsocial hours and worse conditions.
Workers are also angry about a derisory pay deal from bosses, which they insist be linked to negotiations over night Tube operation.
Both the Aslef and RMT unions have confirmed they are preparing to ballot their members for strikes.
The TSSA union was yet to announce a ballot as Socialist Worker went to press.