PASSENGERS have criticised a rail operator amid claims commuters are struggling for places on shorter trains on a flagship service between Scotland's two largest cities at peak times.

Commuters have said too few carriages are being laid on by operator ScotRail under franchise holder Abellio between Glasgow Queen Street and Edinburgh Waverley in the morning on weekdays.

A number of passengers have raised concerns and the problem has also been identified by a support group.

One passenger said the service between 8am and 8.30am from Glasgow "resembles the last plane out of Saigon" in a reference to scenes at the end of the Vietnam War.

ScotRail said it makes the best use of its rolling stock but added sometimes fewer carriages may be available.

Mick Cash, of the RMT union, said it had raised concerns over the service since Abellio took over the multi-billion pound franchise to run Scotland's train services for the next decade earlier this year.

The firm, which beat Aberdeen-based First Group for the franchise, pledged to invest in the Scottish service and introduce high-speed trains on services including Aberdeen and Inverness, free wifi on trains and nearly a quarter more carriages across the network.

Mr Cash said: "This is yet another example of a private rail company promising the earth and then hacking back services to the public at the first opportunity to maximise profits.

"Passengers are right to be angry that they are being crammed into short formations and they should take their complaints straight to the Scottish Government who awarded this contract despite all the warnings from RMT."

A ScotRail spokeswoman said: "New electric trains will provide additional capacity and cleaner, greener journeys from 2017 as part of the wider electrification project.

"In the meantime we seek to make best use of train carriages at our disposal and match demand with supply as far as possible.

"From time to time we have to make changes at short notice which means that some services may fewer carriages than normal on occasion."

One traveller said: "The 8.15am Glasgow Queen Street to Edinburgh Service is always packed full of commuters between the two cities.

"First Group had six carriages. Now, it's three carriages and it resembles the last plane out of Saigon when it leaves Queen Street.

"You have people who are spending more than £100 per week and they're being forced to stand.

"By the time it reaches Linlithgow, you feel claustrophobic with the sheer volume of people. Staff have told me that the train is going to be run as three carriages for the immediate future."

He added: "Meanwhile, seats in the first class section remain empty.

"Conductors tell people who try to alleviate the crowding by sitting in first class to upgrade to a first class ticket or put up with standing in cattle class."

Robert Samson, a Transport Focus passenger manager, said: “It can be very frustrating for the passengers that have to use a short-formed service, particularly because they can be very overcrowded.”

Abellio is suffering wider troubles after the recent departure of Jeff Hoogesteger for his role in a scandal engulfing the Dutch firm.

Mr Hoogesteger was dismissed following claims of irregularities at the State-owned Dutch Railways Nederlandse Spoorwegen.

Ministers have faced calls for an inquiry over the Dutch firm's Scottish franchise.