Michael Mansfield QC said the prisoners themselves could not have cut the perimeter fence wires to ease their escape and added that vital video evidence that showed who did was missing. Only prison officers normally had access to that area.
Mr Mansfield urged Michael Howard, the Home Secretary, to call another public inquiry into the escape in September 1994. All the men were recaptured within two hours but the incident revealed lax security and prompted a complete review of prison security.
The dramatic claims, which were immediately rejected by the Prison Officers' Association, came after the trial of the six men was abandoned because the London Evening Standard newspaper published a report which was potentially prejudicial in the case.
It was the second time that a trial against the men, all category A prisoners, had been halted and the judge, Mr Justice Kay, recommended a third trial would not be in the interests of justice.
The six - IRA men Paul Magee, 48, Gilbert McNamee, 36, Liam O'Duibhir, 34, Peter Sherry, 31, and Liam McCotter, 33 - along with an armed robber, Andrew Russell, 34, had been charged with breaking out of prison, and possessing a firearm with intent to endanger life.
Speaking after the case, Michael Mansfield, who was defending Liam McCotter, said that film evidence of their attempted escape which should have been taken automatically by cameras around the jail had never been found.
"These vital minutes" which were missing pointed to collusion of prison officers directly involved in the break-out, he said. The end of the trial proceedings meant "this whole matter has still not been resolved".
Mr Mansfield said this was particularly important as Whitemoor was regarded as a flagship of a new tougher regime.
"If the taxpayer is going to be asked to fund such prisons as this, they are entitled to know how it is that an escape of this kind can be engineered."
But John Boddington, chairman of the Prison Officers' Association, said he "totally refuted" any prison officers' involvement.
"It was prison officers who discovered the escape and quickly brought it to an end. If there is any evidence of any third-party involvement, they should bring that evidence to the police very, very quickly."
A Prison Office spokesman also urged Mr Mansfield to take any evidence that had not yet been investigated to the police. Michael Howard said that the breakout had been thoroughly examined by Sir John Woodcock in a report published in December 1994.
The recommendation from Mr Justice Kay that a third trial of the escapers would not be in the interests of justice prompted the Home Secretary to announce he was considering allowing prosecutors to seek reviews on decisions which brought a case to a conclusion contrary to the prosecutor's submission.Reuse content