Rail passengers travelling between the north-east and Central Belt will face a “free-for-all” if plans to remove seat reservations go ahead.
ScotRail has announced temporary plans to suspend reservations on its inter-city routes from December 15 due to a delay in the arrival of new high-speed trains.
The issue means there are three types of trains currently operating on the route, all with different seating configurations.
ScotRail bosses say that means they are unable to say for sure which type of train will be operating on particular services at the time advance tickets go on sale.
Mick Hogg, RMT’s regional organiser for Scotland, said: “Passengers will be frustrated and angry that this policy is being applied.
“The staff who actually deliver on behalf of ScotRail are being treated with absolute contempt and are ending up paying the price because passengers are unable to reserve seats.
“Passengers are going to end up in a free-for-all for seats if there are no set reservations.
“There are a lot of problems with this policy and we are asking ScotRail to reconsider, because it is a recipe for disaster.”
The independent watchdog Transport Focus called on ScotRail to show it can deliver the policy safely.
Senior stakeholder manager Robert Samson said: “Groups such as families will be disadvantaged, as will elderly passengers with luggage.
“ScotRail must have robust measures in place to ensure that the proposed ‘counted place’ measure works, that vulnerable passengers are protected and that the availability of advance purchase tickets is not reduced as a consequence of no seat reservations.
“We would urge ScotRail to reconsider this move and clearly demonstrate how this change will make life easier for passengers as is intended.”
A ScotRail spokesman said: “We have been badly let down by our high-speed train suppliers Wabtec and Angel, which means we don’t have as many upgraded trains as we should have had at this point.
“Because of this, unfortunately we aren’t able to provide a consistent level of service to our customers.
“As a result, for an interim period of time we have replaced reservations. Importantly for our customers, we will continue to sell the cheapest advance tickets and manage quotas on our trains.
“The work we have carried out to monitor customer numbers on these key inter-city routes over the previous few months means we are confident that this will provide customers with a more consistent level of service.”
The affected services will be those running between Aberdeen and Glasgow, Edinburgh or Inverness.
North-east Labour MSP Lewis Macdonald said: “What is being proposed will severely disadvantage people travelling from the north of Scotland and the Central Belt.
“The idea that at the busiest time of the year they are making it harder for people to reserve seats is just absurd.”
Liberal Democrat MSP Mike Rumbles added: “This is not the way to deliver a rail network fit for the 21st Century.”
Conservative Liam Kerr said: “I think this raises obvious issues around accessibility.
“The ability to book an aisle seat, or one near the toilet, can be crucial for some people.”
Aberdeen Central MSP Kevin Stewart said: “I can’t see why having three different carriages means that seat reservations have to be removed.
“Let’s hope common sense prevails and ScotRail chiefs find a different solution.”