The collapse of the Jubilee Line fraud case will be the subject of an inquiry and the situation must never be repeated, the attorney general says.
Lord Goldsmith expressed 'disquiet'
Lord Goldsmith predicted the decision to abandon the case would cause "great public disquiet as it causes me considerable disquiet".
Crown Prosecution Service inspector Stephen Wooler will head the inquiry.
Earlier on Tuesday, Lord Chief Justice Lord Woolf, issued a new protocol for dealing with lengthy trials.
In a written ministerial statement, Lord Goldsmith said: "The public are entitled to an efficient and effective criminal justice system and cases such as the present one must never be allowed to happen again.
"Most serious allegations have not in the end been brought to a final conclusion.
"Very considerable public money has been expended. Much time for a jury and for judge and defendants has been expended.
"It is important to learn what lessons we can."
The scope of the review would be drawn up soon, he added.
And he stressed a new system has been devised by the CPS to handle large and complex cases.
The CPS itself has called on the criminal justice system to "learn from this experience and that the exceptional circumstances that brought it about are never repeated".
CPS casework director Chris Newell said it was a matter of "grave concern such an important prosecution should end in this way".
But he defended jury trials in complex cases.
As the allegations were serious, he believed it was clearly in the public interest to bring them before a court and jury.
The Legal Services Commission has defended the cost of legal aid for the defendants at just under £14m.
The commission's Richard Collins said the complex nature of the case, volume of documentary evidence and length of the trial were behind its high cost.
But he said they had been managed and controlled through special arrangements introduced since 2001.
"In the absence of such arrangements, defence costs would have been considerably higher," he said.
The British Transport Police initiated the investigation and has defended bringing the case to court.
It said the Jubilee Line extension project was, at the time, the biggest civil engineering project in Europe - with contracts being awarded for more than £2bn.
The investigation was complex and inevitably lengthy, it said, but said the time spent on it showed "police determination not to be soft on 'white collar' crime".
Factors leading to the trial being halted were "beyond our control" a statement said.