The bidders include:

-  Stagecoach Rail Projects

- a joint venture of Keolis UK and Amey Rail

- a joint venture of Go-Ahead and Colas Rail, and

- Serco

Expressions of interest were invited last July and TfL says it will issue a formal invitation to tender to within the next few weeks. A preferred bidder will be selected by the middle of next year.

Since April 1997 the DLR has been operated by Serco, which was awarded an 18-month extension to its current contract in January this year.

The 38km driverless network has 45 stations and played a key role in providing transport for the Olympic Games, which pushed passenger numbers beyond 100 million for the first time last year.