The RMT union has extended its strike mandate on the London Underground for a further six months, raising the possibility of further disruption.
Tube workers voted to continue the campaign in a long-running dispute over jobs, conditions, and pensions.
The RMT said 95% of its members voted in favour of continuing strikes on a 54% turnout.
The union will now consider its next steps in the campaign.
RMT general secretary Mick Lynch said: “I congratulate our members on delivering another impressive Yes vote in our campaign on pensions, jobs and working conditions on London Underground.
“Our union will now consider the results and the next steps in this campaign.”
RMT had planned to take strike action last month, but this was suspended after “significant progress” over job changes and changes to rosters, however, wider negotiations are still continuing over pensions and working agreements.
Last month 37 hospitality brands, including Wasabi, Greene King and Rosa’s Thai, signed an open letter in partnership with UKHospitality urging rail unions not to strike during the festive period.
The managing director of Dishoom said he was fearful the group could lose 3,500 bookings over Christmas if there were further train strikes during the festive period.