Former rail regulator Tom Winsor has said the government paid "scant regard" to the legal implications of its moves leading up to Railtrack's collapse.
Mr Winsor says the government threatened direct political control
Mr Winsor told the BBC the government threatened him with legislation to stop him offering Railtrack a lifeline.
Railtrack shareholders are claiming £157m in compensation, arguing that the government plotted the firm's demise in 2001 by refusing it extra money.
The government has said it did not engineer the collapse of the company.
Mr Winsor's comments follow the adjournment 11 days ago of the Railtrack shareholders' case against the government.
Central to the shareholders' case is that the government did not properly consider ways in which the company could have continued to operate, because it secretly wanted to renationalise it.
Mr Winsor said the government threatened to take his office under direct political control, in order to block the channelling of potentially billions of pounds of extra money into Railtrack.
He said that by doing so, ministers tried to "neutralise" the power of an independent authority, which was a central plank of private sector investment in the industry.
Mr Winsor said that Railtrack's management was convinced an emergency review that could have brought in more cash and helped stave off administration could not be carried out in time to save the firm.
"They (Railtrack) said unless I could complete a review in 24 hours and put the money in their account...there was no point in starting the review," he told the BBC's Today programme.
"I found that quite extraordinary but that is the position that they took."
A spokesman for the Department for Transport said the decision to put Railtrack into administration was made by a High Court judge, not the government.
But Mr Winsor said: "If I had seen the papers that were put in front of the judge the next day - and I only saw them a few days after the order was made - I would certainly have reviewed on my own motion and without Railtrack's request."
A judgement on the shareholders' case will be made in October.