The Government has been accused of "smashing apart" a key rail line over its plans to "bulldoze through" its re-privatisation.
The Rail, Maritime and Transport union (RMT) said it had seen a copy of the prospectus for returning the East Coast Mainline to a private operator.
The line, which runs through Stevenage and Peterborough, has been run in the public sector since autumn 2009 but is due to go back into private ownership in early 2015.
The union said the document redacts sections highlighting the good punctuality and performance of the service under public ownership.
Campaigners and rail union chiefs today handed over a petition to stop the East Coast line being re-privatised, to shadow rail minister Lilian Greenwood and Green Party MP Caroline Lucas, signed by more than 23,000 rail passengers.
RMT general secretary Bob Crow said: "This leaked document, coming on the day of union protests at Parliament aimed at keeping the East Coast in public ownership, is political dynamite which blows the lid off the lengths to which the Government are prepared to go to bulldoze through re-privatisation before the next election.
More than 60 MPs from Labour, the Liberal Democrats, Green and Scottish National (SNP) parties have signed an early day motion calling on the Government not to re-privatise the line
Campaigners have highlighted figures announced last week which showed that East Coast paid #208 million in premium and dividend payments to the Treasury in the last financial year (2012/13).
Its turnover increased by 4.2% and it carried more than 19 million passengers - up 1% on the previous year.
The campaigners also point out that figures from the Office of Rail Regulation show that East Coast received the lowest public subsidy of any rail operator by some considerable margin.
In addition, those keen to keep East Coast publicly run say that the Government is rushing through this particular re-franchising so it takes place before the 2015 general election.
A Department for Transport spokesman said: "The independent Brown Review into rail franchising was clear that franchising remains the best way to secure services for passengers.
"A strong private-sector partner will not only provide certainty of ownership for the East Coast franchise but will be best placed to build on the significant investment planned for the route, delivering benefits to passengers and taxpayers for years to come."