Virgin Trains have moved forward with court action against the decision by the government to award the West Coast Main Line contract to FirstGroup.
The legal action is aimed at forcing a judicial review of the procurement process.
Pressure has also been placed on the government from Labour, who want a delay on the decision, so that MPs can review the contact.
Founder of Virgin Group, Sir Richard Branson, commented: "In the bid process the one thing we do know is our bid was voted far more deliverable than FirstGroup's.” and “we're absolutely convinced they've got their maths wrong with FirstGroup.”