Workers at the National Gallery in central London, the National Museum of Wales and National Galleries of Scotland are set to strike together next Saturday.
The PCS union members at the National Gallery were on their eighth day of all-out strike as Socialist Worker went to press.
They are striking to defend their terms and conditions following a privatisation deal.
Meanwhile PCS members at National Museum of Wales’s seven sites have been fighting plans to scrap premium payments for weekend working.
A strategy of rolling strikes across Wales starting from Wednesday of this week is set to climax with a walkout at all sites next Saturday.
And PCS members at National Galleries Scotland were set to begin a seven-day strike from this Monday over a similar dispute.
So workers at galleries and museums across Britain could all strike on the same day.
The National Gallery strikers are also fighting for the reinstatement of victimised union rep Candy Udwin.
Candy was suspended and later sacked for drafting a question about the cost of hiring private security firm CIS.
The gallery had brought in CIS security guards to staff its Sainsbury Wing.
Candy’s appeal hearing concluded on Tuesday of last week. But she had still not been notified of the result as Socialist Worker went to press.
PCS officials were set to meet for talks with new gallery director Gabriele Finaldi on Thursday of this week.
Finaldi had just started as director this Monday. He briefly spoke with Candy before crossing the picket line on Tuesday.
The National Gallery strikers have received widespread support.
Candy told a picket line, “We’ve closed more rooms in the gallery since we’ve gone all-out.
“We’ve had more support on our picket lines. And we’ve had more people signing the petition.”
The possibility of coordinated action next Saturday puts them in an even stronger position.