More than 10 ScotRail trains were taken out of service permanently amid delays and cancellations on the network in recent weeks.
The rail operator said 11 trains were sent south of the border after their lease expired on December 12.
READ MORE: The 12 days of Christmas chaos at ScotRail: New calls for an end to Abellio's 'disastrous reign
Liberal Democrat leader Willie Rennie described the situation as a "huge forward planning failure".
A delay in new Hitachi trains being sent to Scotland, an industrial dispute and a shortage of train crew due to training has caused hundreds of delays and cancellations since the start of the month.
Mr Rennie said: "With the new timetable launching and the Scottish rail network struggling, it is astonishing that ScotRail chose this moment to hand back six 158 class trains to Northern Rail. This seems like a huge forward planning failure.
"The result means chaos for commuters at Dalmeny, Fife and Inverkeithing, who found there was no room for them to get on to shortened trains.
"Why on earth are ScotRail handing back trains when all the new trains haven't even arrived yet?
"It also begs the question why the First Minister and (Transport Secretary) Michael Matheson failed to mention this when they were challenged in the Scottish Parliament this week.
"Passengers just want trains to be reliable and value for money but recently they've been getting neither.
"The Transport Secretary must address the catalogue of errors and mismanagement that has been holding up Scottish passengers."
ScotRail said the trains being removed was factored into the new timetable change which came into force on December 10, and they were leaving to free up space in the depots for new and refurbished trains.
However, the operator was unable to say how many services had been cancelled in the week the trains were sent south.
A ScotRail spokesman added: "We know that one of the biggest concerns for our customers is busy trains - we do all that we can to meet demand, which can peak at different times.
"We run over 2,400 services every single weekday and every available train we have is out on the network to get our customers where they need to be."
"Next year, we will begin to redeploy more of our existing Class 170 trains to Fife and the Borders. These trains will add more than 5,000 extra seats each day."
The row comes a day after Nicola Sturgeon said delays caused by ScotRail were "not acceptable" when speaking at First Minister's Questions.
She said the railway operator caused 144 cancellations on Monday and 40 on Thursday.
A Transport Scotland spokeswoman called for the UK rail review to consider devolving all rail matters to Scotland.
She said: "The structure of the rail industry, including the requirement for franchising which drives these rolling stock transfers, is reserved to the UK Government.
"Efforts have been made to lessen the impact of trains going off lease, examples being the lease of c365s as a short-term measure to alleviate the impact of late delivery of the new c385s and keeping more of the class 170 fleet."
She said seating capacity will rise by 23% by next December through the Government's £475 million investment during the franchise, but added it is "disappointing" the "full benefits" of this have not yet been realised due to late train deliveries.
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