Adding in the cost of taking over its £8.4 billion pension deficit, it means that the bill to the taxpayer of selling off Royal Mail could be more than £10 billion.
The news came as plans to privatise Royal Mail were formally agreed by Parliament. The sale could happen as early as next year.
Ed Davy, the postal services minister, confirmed a report in The Daily Telegraph last month that an extra bail-out is needed of Royal Mail. Mr Davy told MPs yesterday said the extra cash was vital to ensure that “the universal service" was protected.
He added: “To do this, Royal Mail needs to be on a sustainable commercial footing. The company currently has around £1.7 billion of debt facilities with the Government.

They should give up on trying to do failed nu labour policies.