The 15-year overnight trains contract which is operated by Serco started in 2015 and is not due to end until 2030, although changes can be made next year.
Scottish Labour’s new transport spokesperson Alex Rowley accused the Scottish Government of “inconsistency and double standards” by not including the Sleeper franchise in its nationalisation plans.
Transport Secretary Michael Matheson announced on Wednesday the ScotRail franchise would be switched to state control in March 2022 when Abellio’s ten-year contract is terminated three years early.
An “operator of last resort” which will be at “arms-length” from the Scottish Government will run the operator.
This is likely to be a temporary measure because the UK Government, which controls the structure of the rail franchise system, has yet to announce its plans to replace the system.
Mr Rowley said not including the Sleeper in Mr Matheson’s plans ”showed a lack of commitment to fully nationalise the railways”.
He said steps must be taken “to bring the two systems under one umbrella”.
Mr Rowley said: “It is nothing short of hypocrisy that the SNP Government would claim to support nationalising our railways whilst leaving the Caledonian Sleeper out in the cold.
“If the Scottish Government is going to nationalise our railways, there can be no half-measures.”
Mick Hogg, Scottish organiser of the Rail, Maritime and Transport union, said: “Any operator of last resort should include the iconic Caledonian sleeper trains.
This Serco mob are as bad as – if not worse than – Abellio ScotRail."
Kevin Lindsay, Scotland organiser of train drivers’ union Aslef, said: “We welcome the fact ScotRail is returning to public ownership but call on the Scottish Government not to leave the Sleeper service in the hands of outsourcing company Serco.
"All of Scotland’s railways should run by the people for the people.”
Manuel Cortes, general secretary of the Transport Salaried Staffs’ Association, said: “Mr Matheson talked a good game on Wednesday about public ownership.
"If he means what he said, he must also bring Caledonian Sleeper’s vital links between the Highlands and key Scottish cities to London back into public ownership.”
A Transport Scotland spokesperson said: “The Sleeper franchise is not currently due for renewal and the focus now is on restoring passenger numbers and revenue as lockdown restrictions are eased.
"Caledonian Sleeper services will make a valuable contribution to sustainable tourism in Scotland.
“As a matter of good practice, the operation of the franchise contract is kept under review to ensure it remains appropriate to meet market demand and passenger requirements.”
The Sleeper franchise was part of ScotRail until it was split into a separate contract in 2015.
The service normally operates trains six nights a week between Aberdeen, Edinburgh, Fort William, Glasgow, Inverness and London.
However, this has been reduced because of the Covid pandemic to the Edinburgh and Inverness routes only.