Specialist staff at three top museums have voted to take industrial action in a dispute over pay.
The National Museum of Film, Photography and Television in Bradford, the National Railway Museum in York and London's Science Museum are affected.
Curators, conservators and managers are angry that a new pay-grading system has been delayed.
Their union, Prospect, says many of its members have missed out on three months of higher pay.
Lack of funding
Some 92% of the 204 union members balloted voted in favour of working strictly to their agreed hours from 16
Alan Leighton, Prospect's national secretary, said the action meant staff would not be working the unpaid overtime which, he claimed, the museums relied upon.
The staff want managers to backdate their pay rises to last September when the new grading system was supposed to be introduced, he said.
He hoped the protest would also draw attention to the "insufficient" level of government funding.
The Department of Culture, Media and Sport had failed to compensate the museums for the extra costs faced since the introduction of free entry, Mr Leighton added.
The museum staff are employed by the umbrella group, the National Museum of Science and Industry (NMSI), which said it was suffering a "worsening financial situation".
An NMSI spokesman added: "We want fair, appropriate and equitable pay for all our staff.
"At the same time, we have to act within the limits of what is financially prudent for us as an organisation and in the public interest.
"We will continue to discuss this with the union and we will do this in a co-operative a manner as we can."