A new operator on the East Coast Main Line could cut the number of first class carriages to provide more seats for passengers on standard fares.
The proposal is included in a prospectus published by the Department for Transport as it fired the starting gun on the contest to find a new private operator to run long distance services on the line.
But trade unions and Labour MPs were furious that Ministers were pressing ahead with the franchise, after the service made profits of £620m under public ownership, which has gone to the Treasury.
The service, which runs for 393 miles between London, Peterborough, Doncaster, Leeds, York, Newcastle and Edinburgh, has been managed by Directly Operated Railways, a company owned by the Department for Transport, since 2009.
Critics of the franchise process argue it should stay that way.
They include Blaydon MP Dave Anderson, who responded angrily when the Government officially launched the franchise contest yesterday.
He said: “I’m disgusted. It is typical of this Government. They don’t pay attention to the people that know best, ie the people that work in the industry and have said this is the best run railway line in Britain.
“And they don’t listen to the people that use the line. I use it twice a week. We have seen huge improvements in the service.”
But Transport Secretary Patrick McLoughlin insisted: “We want to see a revitalised East Coast railway, one that both rekindles the spirit of competition for customers on this great route to Scotland and competes with the West Coast on speed, quality and customer service.
“We need a strong partner to ensure we successfully deliver the £240m programme of infrastructure investments on the route and the improvements in rolling stock that the multi-billion Intercity Express programme will provide.”
While the prospectus sent out to potential bidders invites rail firms to draw up their own plans for the line, it also highlights a number of ideas for them to consider.
They include cutting the number of first class carriages to provide more standard class seating.
Proposals include requiring the operator to transfer some of its profits into a “customer and communities fund” to back non-commercial projects along the route.
The franchise holder will also be expected to develop ways of integrating its ticketing system with other forms of public transport, possibly leading to the expansion of “smart ticketing” systems such as cards which work on trains and buses.
The prospectus also highlights plans to introduce faster trains built in the North East - although this is due to happen regardless of the franchising process.
But rail union RMT said the Government was inviting private firms “to exploit the East Coast service for their own gain”.
RMT General Secretary Bob Crow said: “It is simply outrageous that the Government are firing the starting gun on the reprivatisation of the East Coast when every objective analysis shows that this is a successful and reliable service contributing a billion pounds back to the Government while the private operators are milking huge profits and soaking up vast taxpayer subsidies.”
TUC General Secretary Frances O’Grady said: “Directly Operated Railways has re-invested profits in improving the service rather than lining the pockets of shareholders.
“The Government doesn’t have one good argument for re-privatising the line and is yet again being blinded by outdated market dogma.”
Anthony Smith, chief executive of the independent watchdog Passenger Focus, said: “We will be watching this closely on behalf of passengers. We are pleased to contribute to the process, strongly advocating that passengers must be put at the heart of all contracts and kept informed on how well the train operator is performing.
“It has never been more important that companies are publicly held to account for their passenger satisfaction ratings - these must be built into the very heart of the contract.
“However, it is good to see the franchise process moving ahead again and unlocking much-needed investment.”