The government's Transport Committee chairwoman has said it is "outrageous" that trains will be moved from the North to the South of England.
MP Louise Ellman has written to the Secretary of State for Transport for an explanation about plans to transfer nine trains to Chiltern Railways.
The trains, currently used between Manchester and Hull, will move from April 2015 in a lease agreement.
The current train operator has "no contractual rights" to the trains.
'North loses again'
First TransPennine Express leases nine of 70 trains that will be transferred as Chiltern Railways required additional trains for its services.
First TransPennine Express said it has rights to the trains from 1 April 2015 as its current franchise ends.
Mrs Ellman said: "It is absolutely outrageous that carriages that are in use in the North on our railways are now apparently to be transferred to Chiltern Railways.
"This is absolutely unacceptable."
She has written to the Secretary of State for Transport "demanding an explanation" and "wants to know what he's going to do about it".
Rail passenger group TravelWatch NorthWest said it was "scandalous" that the trains will be moved to the South of the country.
John Owen, from TravelWatch North West, said: "First TransPennine Express is already the most overcrowded train company in the UK and will now lose 13% of its train units."
"The North loses again and rail passengers here can look forward to continuing overcrowding misery for the foreseeable future," he added.
But the Department for Transport (DfT) said replacement trains would be leased so that services can continue.
A DfT spokesman said: "We are working with TransPennine Express to ensure passenger services are not affected by the commercial agreement between the train owner, Porterbrook, and its customer Chiltern Railways."
First TransPennine Express managing director Nick Donovan added: "One of the subjects that will be addressed by these negotiations is rolling stock capacity in order to maintain the significant capacity and timetable improvements that we will bring in from May this year."
The train operator is in negotiations with the DfT for a new longer term rail franchise from February next year.