A DOZEN trains used by ScotRail have been moved to England despite services in Scotland facing chronic overcrowding.

Northern Rail has already taken charge of half of the fleet after ScotRail's lease expired, with the rest due to go south by the end of 2018. This is despite frequent complaints from commuters about overcrowding on Scots trains and a lack of carriages on services.

Last night, a transport union blasted the move as "bad management" by ScotRail's Dutch-owned operator, Abellio.

"As summer approaches, passenger density gets higher so it's no time for Scotland to be losing trains from the service," said Manuel Cortes, general secretary of the TSSA union.

The dozen ScotRail trains served routes between Scotland's Central Belt and Aberdeenshire. Northern Rail runs services in English regions, including the north-west and north-east, as well as in Yorkshire and Humberside.

After ScotRail's lease on the trains expired with leasing company Porterbrook, the firm agreed a deal for the dozen-strong fleet with Northern Rail.

Cortes said ScotRail's owners should have fought to retain the lease on the 12 trains before the deal with Northern Rail. ScotRail has faced capacity problems due to delays with the delivery of a fleet of new Hitachi c385 electric trains, which were set to come into ScotRail service in May.

A spokesman from Scotrail Alliance - a partnership between Abellio and infrastructure owner Network Rail - insisted it was seeking to increase the number of trains available, saying: “The work we are doing now to secure more trains will mean customers will benefit from more capacity than was previously available.”

However, Cortes said the UK's privatised railway system allowed the leasing companies to make profits at the expense of passengers, who had been let down.

"Bad management by Abellio is partly to blame," he said. "But the lease system of trains is one of the most snide and despicable things about the great rail privatisation swindle.

"They are not owned by Network Rail or even the train operating companies but by private venture operating companies who just lease old trains - the very same ones that we use to own in public ownership - to the highest bidder, for rip off rates.

"We must take Scotland's railways into public ownership so that they are run for the Scottish people by the Scottish people, at the service of them rather than speculators.

"This means directly owning the rolling stock."

Cortes called on the Scottish Government to use its powers to nationalise rail in Scotland.

He said: "Of course, this debacle is entirely avoidable if the SNP had the courage of their convictions and booted the private companies out of our industry.

"Until this is done, I'm sorry to say that the crisis of failing trains and let down passengers will continue."

However, the Scottish Government said that Holyrood does not have sufficient powers to renationalise rail. Transport Minister Humza Yousaf has insisted he will deliver on the SNP's 2016 manifesto pledge to ensure a public sector bidder is in place to bid for railways when the contract comes up for renewal.

The Scottish Government added that ScotRail was seeking to lease additional trains to increase space for passengers.

“ScotRail have been working hard to finalise an agreement on the lease of a number of c365s which will help ensure the best available capacity while we await the arrival of the new c385 trains," a spokesperson said.

"In fact, the first of these could potentially arrive in Scotland in the coming days for testing and driver training."