Staff at the National Gallery in London are to stage a five-day strike in a row over the privatisation of services.
The walk-out, over plans to hand visitor services to a private company, will run from 3 to 7 February.
Last week the Public and Commercial Services (PCS) union said its members had voted by more than nine to one for industrial action.
The National Gallery said the proposed changes were "necessary" and that it was "disappointed" by the strike vote.
About 250 workers are involved in the dispute over the gallery's plans, which PCS general secretary Mark Serwotka has called "reckless".
"This five-day walkout will put the National Gallery in the spotlight for all the wrong reasons," he said.
"The sell-off plan... risks damaging the worldwide reputation of what is one of the UK's greatest cultural assets."
According to the union, the National Gallery plans "to privatise almost all staff, including those who look after the paintings and help the gallery's six million annual visitors".
"They have also reneged on a promise to introduce the London living wage, meaning the institution is the only major museum or gallery in the capital that does not pay it."
In its own statement, the National Gallery insisted its modernisation plans would entail no job losses while enabling it to operate with "greater flexibility".
It said it expected to remain open throughout the industrial action, though all planned education events during the strike period would be cancelled.