Tube workers are set to hold a series of Metropolitan Line strikes in January and February.
Rail union RMT announced the action this morning - January 10 - in response to what it called "outrageous imposition of rosters by London Underground bosses".
The planned strikes come amid an ongoing dispute over driver rotas which has already seen walk-outs over the past two months.
The union said the latest decision follows an "overwhelming" vote for action by drivers on the Metropolitan line based at the Neasden Depot.
RMT general secretary Mick Lynch said: "There's a toxic culture developing at London Underground which amounts to the wholesale ripping up of normal procedures and agreements and our members at Neasden have said loud and clear that enough is enough.
"I am calling on tube bosses to get a grip and stop this wholesale undermining of normal industrial relations."
Mr Lynch added that the union remains "available for talks".
The Metropolitan line strikes are planned to take place from 11:30am on January 20 to 11:29am on January 21.
More action is expected from 11:30am on February 10 to 11:29am on February 11.
A Transport for London (TfL) spokesperson said: “We’re disappointed that the RMT has confirmed strike action at Neasden Depot and will be talking with them this week to resolve the matter.”
Update: The Metropolitan line strikes planned for January 20 and January 21 have been suspended.
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