Rail services could be disrupted from Christmas eve as signal workers in Scotland stage a 72-hour walkout in a row over career progression.

The Rail Maritime and Transport (RMT) union claims Network Rail managers have ripped up long-standing arrangements under which staff were "slotted" into a post when it became vacant. It said the arrangement had been in place for more than 30 years.

The union confirmed last week that members based at the West of Scotland signalling centre will stage a three-day strike from Saturday. The company said the dispute only affected 32 staff based at the West of Scotland centre but the union said it involved more than 50 of its members.

RMT general secretary Bob Crow said: "RMT has tried to reach a negotiated settlement to this unilateral ripping-up of a local arrangement but unfortunately the management have refused to see sense and RMT members will not stand by while management tear up agreements and practices that have been in place at local level for decades.

"As a consequence of management's intransigence, we have no option but to go ahead with this strike action. RMT members are furious at this refusal to comply with a local arrangement that offers genuine career progression opportunities. RMT remains available for talks at any time aimed at resolving this dispute."

Network Rail has disputed the union's claims that staff being "slotted" into vacant posts was a long-standing agreement at the centre and said it did not consider any agreement had been breached. It insisted that the method had not been a recognised agreement for filling posts since railway privatisation in 1994.

A spokesman said: "Network Rail does not consider that any agreements have been breached - slotting is an outdated practice which has not been recognised since privatisation. We feel that appointing on merit rather than just seniority is a reasonable ambition in the 21st century workplace.

"We are disappointed the union is attempting, through its choice of dates, to disrupt Christmas travel, but are confident we can still run a full service."

Network Rail also issued a statement which said: "The union claims that it has tried to reach a negotiated settlement - again, this is untrue. The RMT has to date not sought any negotiated settlement. The issue has been escalated from an individual grievance to a strike ballot completely bypassing the collective bargaining arrangements in place."

ScotRail said some services running to and from Glasgow Central will be withdrawn or less frequent as a result of the strike.

A spokeswoman said: "This action is beyond the control of ScotRail and we apologise for any inconvenience caused. We have published a summary on our website and put up posters at stations. Everyone should check their journey before they set out, in particular noting their last train home."