A contract to run trains between London and Scotland has been awarded to a Stagecoach and Virgin joint venture.
The move will mean that the East Coast line will once again be in private hands, after being controlled by the state for the last five years.
Virgin and Stagecoach have vowed to invest £140m in the project over eight years, but they will have to fork out £3.3bn to the UK government for the contract.
Transport Secretary Patrick McLoughlin said: "This is a fantastic deal for passengers and for staff on this vital route. It gives passengers more seats, more services and new trains.
"We are putting passengers at the heart of the service. I believe Stagecoach and Virgin will not only deliver for customers but also for the British taxpayer."
However, RMT general secretary Mick Cash said that the decision to put the contract back in private hands was "an act of utter betrayal".
"The government has confirmed that it is bulldozing ahead with the re-privatisation of the East Coast Main Line despite all the figures showing that the current public sector operator is handing over a billion pounds back to the British people while delivering huge improvements in service and customer satisfaction," Cash told the BBC.
The East Coast line was nationalised in 2009 after National Express, the previous operator, built up huge losses on the routes and decided to hand it back to the state.
FirstGroup, Eurostar and French company Keolis had also made a joint bid for the contract.