American construction group Bechtel has been reappointed to oversee the completion of the West Coast Main Line scheme.
The firm was originally brought in by Railtrack in February 2002 to take control of the scheme, the budget of which had risen from £2bn to £7.6bn.
A spokesperson for Network Rail, the successor to Railtrack, said it had exercised an option to extend the Bechtel deal by four years to 2009.
The scheme is due for completion in 2008. The Network Rail spokesperson said that Bechtel would also be responsible for the line during the “winding-down period” when the scheme is finished.
The project began in the mid-1990s and was expected to deliver 140 mph trains on the London-to-Glasgow line by this year. The project has since suffered a series of delays and the proposed speed of the trains has been reduced to 125 mph.