Staff at Royal Museums Greenwich are planning further strike action amid a long-running dispute over pay, terms and conditions.
Prospect members will walk out of the museum on 31 October if remaining demands are not met by management, warned the union, which has more than 300 members at the charity.
The museum, which has a total of 551 staff, runs the Royal Observatory, the National Maritime Museum, Cutty Sark and the Queen’s House art gallery.
Union members previously went on strike for two days in August, resulting in the closure of some sites and the cancellation of a number of events relating to the solar eclipse.
Prospect said some progress has been made in negotiations with management, particularly over the use of fixed-term contracts and annual leave.
But the union said it was frustrated with the “absence of binding commitments and timelines”, which it said risk undermining the agreement.
The museum said the negotiations so far had produced a two-year pay settlement covering 2026/27 and 2027/28, which have been agreed by the union and implemented.
The union said the outstanding issues include concrete plans and timeframes on the museum’s commitments to: write a new annual leave policy; accredit for London Living Wage in 2028; and make sure security workers can take their breaks.
Prospect members are also asking for guarantees that the museum’s new professional development framework will cover non-mandatory training.
The union said it hoped management will agree to its outstanding demands so the strike can be called off.
Mike Clancy, general secretary of Prospect, said: “Our members have shown great solidarity in this dispute, and have already achieved some tangible wins, and they are determined to see this through and secure these reasonable demands.
“We hope that management see sense and put forward acceptable proposals on the remaining disputed issues rather than risk a continuation of industrial action.”
Royal Museums Greenwich said it continued to be in “constructive negotiations” with Prospect.
“The remaining areas of dispute relate to a small number of non-pay matters on which the union and RMG have held meetings and RMG made a series of commitments, including engagement with the London Living Wage Foundation.”
The charity said it had received notice of strike action on 31 October, adding: “We are surprised by this outcome, particularly given the progress which has been made.”
The museum planned to keep its sites open to maintain service provision to the public, it said.