The Tube's East London Line is to shut for two years to allow for a major £1bn upgrade, BBC London has learned.
The East London Line will shut for two years
A leaked London Underground memo shows plans for it to be the first Tube line to be run by the private sector, once work is completed in 2009.
The line, which will play a major 2012 Olympic role, will shut in December 2007 for work to be carried out.
The Shoreditch to New Cross line will be extended north to Highbury and south to West Croydon and Clapham Junction.
Once completed it will be handed to a private operator in 2009 when it will be tied into services on the overland North London Line - creating a new franchise.
Currently only the Docklands Light Railway is run by a private operator - with Transport for London overseeing the contract.
The mayor's office have made the decision to make the East London Line privately-run, said BBC London's Transport Correspondent Andrew Winstanley.
Previously mayor Ken Livingstone had been bitterly opposed to any form of privatisation on the Tube - fighting an unsuccessful campaign against the privatisation of maintenance on the Underground.
The Rail, Maritime and Transport (RMT) union said they were unhappy at the plans and intended to fight privatisation.
A Transport for London spokesman said it would continue to set fares and the frequency of services, and would offer a better service and more jobs under an integrated rail service.
"There will be absolutely no redundancies and all current staff will be offered alternative positions within London Underground in full consultation with trade unions," he added.
The East London Line, currently a relatively short line, carries an average of 34,443 people on a weekday.