Virgin Rail Group has been granted a six month extension to its contract to run the rail link between London and cities in northern England and Scotland, transport minister Theresa Villiers said.

The government said in May that it would delay the start of the next 14-year contract to operate the key West Coast rail connection between London and Manchester to December 2012 from April 2012 to enable ministers to consult on the terms of rail franchises.

The incumbent operator, a joint venture between Virgin Group and transport group Stagecoach, is vying with three other groups, Keolis, FirstGroup and Abellio, to secure the new West Coast deal.

During the course of its extension, Virgin Rail Group will add three new 600-seat trains to the line and other trains will be lengthened, said Villiers.

This will relieve crowding on some of the busiest parts of the West Coast Main Line which is one the UK economy's most important transport corridors, she said in a statement on Thursday.

The government said in August that it was committed to a major reform of rail franchising which would seek to benefit passengers and taxpayers.

A lack of incentive to supply extra capacity on routes is one of the criticisms which has been levelled against the current set up.

Stagecoach and another UK operator, Go-Ahead recently lost out to a Dutch group on a potentially lucrative contract to run Britain's Greater Anglia rail franchise.

(Reporting by Sarah Young; Editing by Paul Sandle)