Museum staff have threaten to walk out as they claim they are not able to sit down on their shifts like those working at other national galleries.
The Public and Commercial Services union said workers at the National Museum of Scotland are being “bullied” by being refused designated seats.
Seats are allowed for staff at attractions such as the Scottish National Portrait Gallery and the Scottish National Gallery in Edinburgh.
Union officials said most museums in major European capital cities, including the British Museum in London, also allowed assistants who spend long periods standing to have their own seating areas.
The dispute comes after the museum was hit by a wave of strikes about the withdrawal of weekend working allowances for the attraction’s lowest-paid employees.
Robert Burns, a PCS representative for Edinburgh’s museum workers, said he had suffered ligament damage by effectively being made to stand for hours on a hard floor at the museum.
He confirmed a ballot on industrial action could take place in the new year over possible strikes at Easter, one of the busiest periods of the year for the museum.
He said about 70 workers would now decide whether to have the ballot, which could involve one-day stoppages or action short of full strikes, such as a work to rule.
Burns said staff had repeatedly been refused designated seats, but told they could use the public seating area, something he said workers felt uncomfortable about doing while they are on duty.
He added management could easily agree to the union request and give staff the same deal as those at other state-run visitor attractions.
A PCS Scotland spokesperson called on National Museums Scotland to agree to the staff seating request.
Labour MSP, Neil Findlay has accused the management of “confrontational” behaviour towards the union and warned the reputation of one of Scotland’s most popular museums could be damaged by the treatment of its workers.
The Lothian MSP echoed the PCS’s call and added: “The National Museum of Scotland is one of our key cultural attractions in Scotland.
Julie Matthews, head of visitor experience at National Museums Scotland, said management had a constructive relationship with the union.