Sir Richard Branson is taking his battle to save his West Coast Main Line rail franchise to the courts.
Earlier this month, the Government announced that Virgin Trains had lost out to transport company FirstGroup in the bidding war to run a new 13-year West Coast franchise from December.
Sir Richard Branson reacted angrily to the decision, branding the bidding process "insane" and threatening to end all involvement with the railways.
Virgin Trains said it was starting court proceedings as it believed the procurement process had "ignored the substantial risks to taxpayers and customers of delivering FirstGroup's bid over the (13 years and four months) course of the franchise."
Virgin now hopes that its legal challenge will delay the imminent final signing of the franchise contract by Transport Secretary Justine Greening.
Labour and the House of Commons Transport Committee have supported Sir Richard's call for a delay to the signing so the matter could be properly debated.
Sir Richard said: "We had hoped that Parliament or an external review would be able to scrutinise this badly-flawed process before the franchise was signed.
"However, that opportunity would be denied if the Department for Transport (DfT) follows through with its determination to rush through the process before Parliament returns next week."
Responding to news of the legal challenge, FirstGroup said: "We have every confidence in the DfT's process which is rigorous, detailed and fair and in which bids are thoroughly tested. There has been no complaint about the process, which was carefully described in advance, until Virgin Rail Group had lost commercially."
FirstGroup went on: "Our plans for the new InterCity West Coast franchise include faster journeys, new trains, more seats and more direct services from London than currently on offer."