A member of the Rail, Maritime and Transport union's executive committee publicly mocked commuters affected by a recent London Underground strike while on holiday in Majorca, social media posts and witness accounts show.

Daniel Gibbons, who represents RMT members in the South East and is seconded to the union's full-time executive, posted photographs and comments from a resort as Tube services across the capital were brought to a near standstill during a five-day action. In one post he shared a clip of a BBC Politics Live discussion in which commentator Anita Boateng described the strikes as "frustrating" and wrote: "Listen to this person so eloquently talk absolute bollocks. It must be a special gift to be that dense. Solidarity to the LUL and DLR RMT members."

Photos posted to Facebook and seen by reporters show Gibbons relaxing in a hotel swimming pool and drinking a pint at Heathrow Airport as commuters in London faced long delays and crowded replacement buses. One person who said they were stuck on a bus responded to a photograph of Gibbons at the airport, to which Gibbons replied: "Solidarity to the LUL members." Another pool photograph bore the caption "floating," with Gibbons replying to critics: "Loving the fact I have them."

A resident of Welling, Kent, who said they had been affected by the strikes described Gibbons's behaviour as "laughing in the faces of all those hardworking people who have been badly impacted by the selfishness of the RMT," and said it risked alienating public support for the union.

An RMT spokesman confirmed Gibbons is seconded to the union's full-time executive and said he had "holiday entitlements like any other worker." The spokesman added that Gibbons "is not a spokesperson for the union and we do not condone abuse of any kind."

The social media posts and on-the-ground reports come amid a dispute over pay and working conditions that forced Transport for London to contend with a reduced service and increased road crowding. The RMT rejected a 3.4% pay offer from TfL and has campaigned for changes to working hours, including a reduction in the current 35-hour week for some members; TfL has said that proposed changes would be unaffordable.

The industrial action affected millions of commuters across the capital, with many services suspended and replacement buses operating on busy routes. RMT members on London Underground Limited (LUL) and the Docklands Light Railway (DLR) were among those involved in the walkouts.

Talks between the union and Transport for London were due to resume Wednesday, the union said, as negotiators sought to resolve differences over pay, staffing and shift patterns. The RMT has maintained that it is seeking improvements for members and argued that its industrial action is a means to that end; TfL has argued that its financial constraints limit its ability to meet the union's demands.

Gibbons's posts drew attention because of his position within the union at a time of heightened public scrutiny of strikes that disrupted travel across London. The RMT statement described his holiday as unrelated to the dispute and reiterated that he is not an official spokesperson for the union, while urging that no abuse be directed at individuals.

The exchange highlights tensions between union activists and commuters caught up in industrial action, and comes as negotiators prepare to resume formal discussions aimed at reaching an agreement to restore full services across the Tube network.