Mr Winsor said the firm had been wrongly convinced by the threats, even though it would have taken 12 months to pass the necessary laws.
He said: 'They believed that and I think that was a disastrous error on their part but that was the judgment they made.'
Almost 50,000 former Railtrack shareholders are suing the Government, claiming it plotted to deliberately collapse the company.
Mr Winsor said that on the eve of Railtrack being put into administration, he offered to set up a review that would bring more cash.
He said: 'The fundamental point is that Railtrack had access to potential billions of pounds of additional money via my jurisdiction as rail regulator,'
'When Railtrack went down, they were satisfied that a threat by former Transport Secretary Stephen Byers to undertake emergency primary legislation to take my office under direct political control was as good as passed.
'It was not. It would have taken a year to pass. It would almost certainly have required the Parliament Act to get it through and until then my jurisdiction would be intact.'
Mr Winsor said: 'They (Railtrack) said unless I could complete a review in 24 hours and put the money in their account on Monday, there was no point in starting the review.
'I found that quite extraordinary but that is the position that
Mr Winsor said he thought a Commons statement from new Transport Secretary Alistair Darling has signalled an acceptance that regulators should remain independent. However, ministers' actions were strongly defended in the court case, the outcome of which will be announced in the autumn.