Labour and rail unions have been among those bitterly opposed to the refranchising of the Scotland to London King's Cross route which has been run in the public sector for four years.
The RMT union has said that the prospectus being revealed today will see a return to "third-class travel" on the line.
The RMT and others have also pointed out that the East Coast has proved a real value-for-money line in that it has returned large amounts of money to the Treasury since National Express pulled out of the franchise in November 2009.
Labour has also expressed disappointment that, with the franchise programme on the railways put back and altered following the botched West Coast franchise bidding process, the Government has appeared to prioritise the refranchising of the East Coast railway line - which is scheduled for early 2015 - for political purposes.
Shadow transport secretary Mary Creagh said: "David Cameron should tackle his Government's cost-of-living crisis and cap rail fare rises for struggling commuters, instead of obsessing about handing East Coast over to the private sector.
"East Coast is working well and will have returned £800 million to the taxpayer by the end of this financial year.
"This Government has learned nothing from the West Coast franchising fiasco, which saw more than £50m of taxpayers' money wasted in compensation to train companies because of ministers' incompetence."
The RMT union has said that it understands the East Coast contract would be awarded "on lucrative, profiteering terms that will enable them to reduce the quality of service [and] introduce a new band of third-class travel".
However it is thought that the so-called "third class" will involve an offer of an airline-style "premium economy" service, between the present standard class and first class.