London Underground workers are being balloted on Tube strikes over pay and conditions amid a dispute with Transport for London (TfL).
Members of the Transport Salaried Staffs Association (TSSA) in jobs including customer service and advising passengers in stations are being asked if they want to strike.
The ballot closes on 18 October and also includes the option to take other forms of industrial action.
London Underground (LU) has made an offer which the union says would see most grades receive a below inflation pay rise, and would freeze most pay ranges.
The TSSA claimed this raised the possibility of long-term, or indefinite, pay freezes.
General secretary Maryam Eslamdoust said: “This situation is wholly of LU’s making, and our members are highly likely to vote overwhelmingly in favour of strike action and action short of a strike.”
She added: “Our intention is to send a strong and clear message to LU that significant industrial action is on the cards across the network unless they are prepared to meet our aspirations on pay, as well as dealing positively with all other aspects of our dispute.
“We always prefer negotiating and only move towards a strike as a last resort, but the ball is now firmly in LU’s court.
“Our members are determined to get the deal they deserve – one which meets the cost of living now and in the longer term.”
TfL has been contacted for comment.
It comes after tube drivers who are members of the Rail, Maritime and Transport (RMT) union voted to take strike action if they deem it essential in the next six months.
While no strikes are planned at present, the mandate could pave the way for further disruption for passengers into early 2025, as pay negotiations continue.