Passengers on a key long-distance rail route have been promised "innovative timetables" and a better travelling experience when the line goes back into the private sector.

The new operators of the East Coast Main Line (ECML) - which is currently being run in the public sector - will also have to demonstrate how they will support economic growth on the Scotland to London route.

Just what will be required of the company which will ultimately run the line was laid down today as the Government officially launched the search for a new operator by publishing an East Coast prospectus.

The line has been run under the control of the Department for Transport (DfT) since National Express pulled out of the franchise in November 2009.

Labour and rail unions have bitterly opposed the reprivatisation of the line, pointing to the fact that East Coast has returned large amounts of money to the Treasury since it has been in the public sector.

Labour has also been unhappy at what it sees as the haste by the Government to get the East Coast line back into private hands even though the whole nationwide franchise programme has been put back and altered following the West Coast bidding process fiasco.

The InterCity East Coast prospectus announced today details what potential bidders will need to consider when they start developing their proposals next year. These include:

:: Developing innovative timetables which build on the core train service requirement published by the DfT;

:: Investment in innovative ways to transform the customer experience on trains and at stations;

:: Identifying further opportunities for investment along the route, particularly at stations;

:: Making the route and train operations more sensitive to the environment;

:: Involving communities along the route in local decision making;

:: Demonstrating how their proposals will support economic growth along the route.

UK Transport Secretary Patrick McLoughlin said: "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 £240 million programme of infrastructure investments on the route and the improvements in rolling stock that the multi-billion Intercity Express programme will provide. "

The Government said today that running the line in the public sector had never been planned to be a permanent arrangement. Indeed Labour, although now cool on the idea, had intended to return East Coast to private ownership when it was in power prior to the 2010 general election.

The new operator will be expected to capitalise on Government investment in this route over the next six years, including the replacement of the current rolling stock fleet, and major infrastructure improvements such as the £72 million programme to improve the line around Peterborough and £20 million enhancements to Doncaster station.

The DfT plans to confirm which prospective bidders have passed the pre-qualification stage in January. The DfT expects to issue the invitation to tender in February. The shortlisted bidders will then have three months to prepare bids, with franchise services starting in February 2015.

East Coast is one of the two main London-to-Scotland railways providing frequent services. It is an electrified 393-mile railway link between London, Peterborough, Doncaster, Leeds, York, Newcastle and Edinburgh.

A non-electrified line extends further north into Scotland from Edinburgh to Inverness and Aberdeen.

Channel Tunnel high-speed train company Eurostar has said it wants to bid for the East Coast franchise in partnership with French company Keolis which already runs a number of UK domestic lines.

TUC general secretary Frances O'Grady said: "The Government has completely lost the plot over its handling of our railways. Since returning to public ownership the East Coast line has flourished, with rising customer satisfaction levels and £800 million returned to the UK taxpayer.

"Directly Operated Railways (the current operators) has re-invested profits in improving the service rather than lining the pockets of shareholders. Ministers have chosen to ignore this and are once more putting the interests of private companies before those of passengers and taxpayers.

"The Government doesn't have one good argument for reprivatising the line and is yet again being blinded by outdated market dogma. As with the Royal Mail, they are putting ideology before evidence in the desire to sell off yet another important state asset."

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."

RMT rail union general secretary Bob Crow said: "It is simply outrageous that the Government are firing the starting gun this morning on the reprivatisation of the East Coast when every objective analysis shows that this is a successful and reliable service contributing £1 billion back to the Government while the private operators are milking huge profits and soaking up vast taxpayer subsidies.

"The prospectus document leaked to RMT was political dynamite which blew the lid off the lengths to which the Government are prepared to go to bulldoze through re-privatisation before the next election, even it means putting up a barrage of lies, distortion and deceit to play down the success of the public model.

"The conman here is Prime Minister David Cameron himself.

"The fact that the public option, which is putting over £1 billion back into the Treasury, while improving services and delivering more capacity, has been cynically airbrushed over by the Government and their officials is a disgraceful piece of political chicanery which must be called in for scrutiny to hold back this full -tilt dash for privatisation."

In the prospectus, presented in a glossy, 48-page brochure, the Government said that despite the economic challenges over the last three years, passenger revenue on the publicly-run line had grown by 11% between 2009/10 and 2012/13 and journey numbers had increased from 18.1 million in 2009/10 to 19.1 million in 2012/13.

The brochure went on: "This growth is reflected in the £620 million which has been returned to the UK Government in premium payments during DOR's (Directly Operated Railways') tenure to March 31 2013."

Then under the heading: "Why are we refranchising East Coast?", the Government said: "Since 1995 the Government's policy has been to allow the private sector to run public rail services.

"State control of rail services is considered to represent poorer value for money, restrict investment and therefore growth and to import risk to the taxpayer. The introduction of competition has been proven to drive improvements for the passenger and leave a lower level of financial and technical risk with the Government. "

The new franchise is set to run for eight to nine years with possible extension of up to two years, "callable at the DfT's discretion".

Responding to the franchise launch today, Michael Roberts, the newly-appointed director general of rail industry organisation the Rail Delivery Group, said: "Successive governments working through Network Rail to invest significant sums in infrastructure combined with commercial operators focused on encouraging more rail use has been crucial to the successful transformation of the railway.

"This partnership between the public and private sectors is a winning formula that is delivering for passengers, businesses and the taxpayer."

Mick Whelan, general secretary of train drivers' union Aslef, said: "The Government is talking about transforming the East Coast. The truth is that the East Coast has been transformed - for fare-paying passengers, for companies, for the people who work on the service, and for the British taxpayer - since it came back into the public sector.

'The Conservatives are driven by a failed ideology - because the truth is that privatisation of the railways in this country has demonstrably failed to deliver - and by a desperation to get a successful public service back into the private sector before they lose the next election."