An inquiry is to be launched after six men walked free when a fraud case costing £60m and lasting 21 months collapsed at London's Old Bailey.
The men were accused of bribing London Underground officials
The men were accused of conspiring to corrupt public officials and gain insider information on a £2bn extension to London Underground's Jubilee Line.
Problems with the jury forced the trial to be abandoned, the prosecution said.
Attorney general Lord Goldsmith said the inquiry would not be a public one - but its findings would be made public.
The move pre-empts renewed calls for such cases to be tried without a jury.
Lord Goldsmith said he expected "great public disquiet" over the case and said it should "never be allowed to happen again".
But, he told the BBC, there was no need for a public inquiry which risked lots more money being spent.
"I have no doubt at all that I will make public the lessons that we learn from this, absolutely," he added.
Speaking outside court, one of the freed men, Mark Skinner, 50, from Warlingham, Surrey, said: "Although I should now feel relief and happiness, I feel only anger."
He said the prosecution had destroyed his business and tortured his family for seven years.
And he accused the British Transport Police and Crown Prosecution Service of "destroying my reputation in order to protect theirs".
The accusations of corruption centred on a surveying company called RWS, owned by two of the defendants, Stephen Rayment and Mark Woodward-Smith.
They were accused of bribing London Underground officials to disclose information which they then used to secure multi-million pound contracts on the Jubilee Line extension.
The pair, both quantity surveyors, and the other four men had denied all of the charges from the outset.
Anthony Upward, QC for the prosecution, requested the trial be discontinued because the evidence was no longer a "living story" and had lost its "immediacy and impact".
The trial has been beset by illness - with defence counsel, jurors and defendant Mr Skinner all having time off.
The jury had also been reduced - one juror becoming pregnant and another being arrested for benefit fraud.
The British Transport Police (BTP), which initiated the investigation, said it stood by the decision to pursue the prosecution.
"The factors that have led to the trial being halted now were beyond our control," the BTP said in a statement.
"The British Transport Police is satisfied that it was in the public interest to pursue the investigation and prosecution."
The six were Mr Rayment, 44, from Leatherhead, Surrey; Mr Woodward-Smith, 44, from Wimbledon, south-west London; Paul Fisher, 52, from Saffron Walden, Essex; ; Graham Scard, 50, from Forest Hill, south-east London; Anthony Wootton, 50, from Stone-in-Oxney, Kent; and Mr Skinner.
The CPS confirmed it will not ask for a retrial.