Britain’s Railtrack says it will go to the High Court to recover £350 million sterling worth of assets, unless the money is freed by 5.30 p.m.
The rail network operator, which is now in administration, claims the British government has failed to give a true account of its funding crisis.
It claims the government cut off a further £445 million in funding which would have given it a lifeline.
Railtrack adds that officials of British Transport Secretary Mr Stephen Byers continued to assure it that revenue grant funding was still available, two days before it called in the administrators.
Finance director Mr David Harding says: "while Railtrack received £336 million on Monday, October 1, as deferred grant, the Strategic Rail Authority did not go forward with the funding structure for the revenue grant also due on that day.
"This would have given Railtrack immediate access to a further £445 million and an equivalent amount over the remainder of its financial year. As late as the evening of Wednesday, October 3, his officials confirmed that this funding structure was still on the table."
The board of Railtrack is considering taking legal action to recover the money - which, if successful, it says could be used to pay shareholders.
It alleges the £350 million has been illegally impounded as the cash comes under the umbrella of Railtrack Group PLC, which is separate from the collapsed Railtrack PLC under administration.
The move offers some hope for angry shareholders, who are facing up to the grim fact that their stakes in the company are likely to be almost worthless.
PA