Ex-Transport Secretary Stephen Byers has said he was not truthful to MPs about the events leading up to Railtrack's collapse.
Mr Byers says he cannot remember why he did not tell the truth
He told the High Court his evidence to a Commons sub-committee was not accurate. He apologised but said he had not been trying to conceal any plot.
Mr Byer's words came on the last day in the case of Railtrack shareholders who are claiming compensation.
Mr Byers denies forcing Railtrack into insolvency to avoid compensation pay.
About 50,000 shareholders claim the government deliberately allowed the rail infrastructure firm to fail in October 2001, and are demanding £157m in compensation.
When Mr Byers was questioned by a Commons sub-committee, he said he was not aware of a change in Railtrack's status being discussed before 25 July 2001.
But in the court on Thursday he was challenged over this version of events by the shareholders' barrister - who produced documentary evidence showing the work had started.
They included e-mails and notes from Department of Transport officials showing that taking Railtrack into administration had been one of the options being discussed as early as June.
Quizzed by Keith Rowley, QC for Railtrack shareholders, Mr Byers admitted his answer to MPs had been untrue.
"It is true to say there was work going on, so, yes, that was untrue," he said.
Questioning Mr Byers again about the "welter of documentation" on the options for Railtrack, Mr Rowley, QC said: "You could not possibly have believed that the answer you gave ... was true, could you?"
"I accept this is not an accurate statement," said Mr Byers.
He was asked if it was "deliberately not an accurate statement".
Mr Byers replied: "It was such a long time ago, I cannot remember, but it is not a truthful statement and I apologise for that.
"I cannot remember the motives behind it."
The MP later told the court he had been under pressure during the hearing and had not set out to conceal any conspiracy or plot.
Responding to Mr Byers' admission, shadow transport secretary Alan Duncan said whatever the verdict in court, the government "will still have to face the verdict of parliament".
"I make no judgement about the court case but it seems from all the evidence that is emerging that this is a growing scandal of government from which Stephen Byers and Gordon Brown have no escape.
"If, as it seems today, Stephen Byers lied to a parliamentary committee, not only is that a disgrace in itself but it shows that their plans for Railtrack were deeply devious and could be a scandal of enormous proportions.
"Whatever happens in court this issue is not going to go away."
'The 10 Commandments'
Mr Byers resigned as transport secretary in May 2002.
At the time, he said he had tried to "behave honourably", adding "the people that know me best know I am not a liar".
Mr Byers has told the High Court the Treasury had concerns about ending Railtrack and removing the role of shareholders.
He said Chancellor Gordon Brown had a list of 10 conditions to be met before he would agree to Railtrack being changed to a non-shareholder company.
The list was internally nicknamed "The 10 Commandments", he said.
At a meeting on 19 September 2001 - three weeks before Railtrack went into administration - Tony Blair told Mr Byers he had to talk to the chancellor if he wanted more money to fund the company.
But the court heard it was left to Mr Byers to decide whether to take the company into administration if he decided to refuse Railtrack's request for more money - subject to the Treasury conditions.
Mr Byers said he had worked with his officials to see if the conditions could be met.
On Thursday, the shareholders QC, Keith Rowley, about when he made up his mind.
"I suggest there was a clear strategy, developed by you and your officials, accepting that Railtrack would not immediately collapse but might fall over in a year or two, to force Railtrack into administration by ensuring you held all the cards and all other options were closed off," said Mr Rowley.
But Mr Byers replied that his discussions with officials were "sensible contingency planning" in case it was decided to refuse to give the company more funds.
There is one more witness to be heard in the court case and lawyers for both sides will spend most of next week delivering their closing speeches.
The judgement in the case is not expected to be delivered until after the court's summer break.