The next operator of the overnight cross-Border service will instead receive £50m of capital investment to upgrade the fleet when it takes over in April 2015, with the remainder of the money siphoned off to pay for other improvements to the rail network.
The UK Government originally made £50m available in its autumn 2011 Budget to replace the sleeper trains, but made this conditional on receiving matched funding from the Scottish Government.
It followed a public outcry over cost-saving measures that would have meant scrapping either the "lowland" service to Edinburgh and Glasgow or the "Highland" service to Fort William, Inverness and Aberdeen.
A deal was subsequently agreed between the governments, but based on refurbishing the fleet of about 50 train carriages rather than replacing them. The money from the Treasury is currently on loan to Scottish Water and due to be repaid to pay for the train upgrade between 2013 and 2017.
However, a prior interest notice published this week by the Scottish Government to alert rail firms of details of the next Caledonian Sleeper franchise, which is being split off from the main ScotRail franchise, confirmed only £50m capital investment would be available.
A Treasury official said the revised terms followed correspondence between Scotland's Finance Secretary John Swinney and Danny Alexander, Chief Secretary to the Treasury. Under this deal, the Scottish Government had agreed to invest £80m but on stations, track and signalling equipment. "The Scottish Government has promised wider improvements to stations at Fort William, Inverness and Aberdeen as well as signalling, stabling at a number of other places," the official said.
Tom Harris, the Glasgow South MP and former rail minister, said: "I suspect there is a sleight of hand and that the money that is used on signalling, track and stations across the network will displace money that was already budgeted by Network Rail for that work.
"Ultimately, it's the customers, especially the Caledonian Sleeper passengers, who have been short-changed."
However, Dave Thompson, the SNP MSP for Skye, Lochaber and Badenoch, said: "As well as investing in improved rolling stock for the sleeper, the planned upgrade will improve on train facilities and improve the services specifically for sleeper passengers at stations, such as waiting rooms and showers, so passengers have the best possible journey. There is far more to the experience of the sleeper service than the carriages."
The Caledonian Sleeper is heavily loss-making and relies on Scottish Government subsidies . Passenger figures revealed by The Herald show this equals about £76 per passenger journey.
A Transport Scotland spokesman said: "As previously announced, we are committed to an investment of at least £100m in Caledonian Sleepers.
"The precise nature of this overall investment – including procurement of sleeper vehicles, services, station facilities, network infrastructure, and other product investment – is yet to be determined."