Justice Secretary Jack Straw was accused today of allowing politics to cloud his judgment over the release of Great Train Robber Ronnie Biggs.
Sir David Latham, the chairman of the Parole Board, said there was no "rational reason" not to release Biggs earlier and attacked the decision to reject the board's ruling.
Mr Straw overturned the decision of the Parole Board and kept Biggs in jail, saying he was "utterly unrepentant".
He later released Biggs on compassionate grounds because of ill health.
Sir David also revealed Mr Straw is to lose the power to overrule the board in future in similar cases.
Biggs is among a number of prisoners sentenced to 15 years or longer before the 2003 Criminal Justice Act came into force.
Little-noticed measures contained within the Coroners and Justice Act, which gained Royal assent yesterday, remove Mr Straw's veto.
The powers could come into force as early as the New Year, a Ministry of Justice spokesman said.
Sir David said: "Jack Straw may well have said 'My gut feeling is that people do not like the idea of a man who has not admitted he has done something really awful [being released]'.
"I think it was a genuine feeling on his part on the way the public might feel about it, but that doesn't necessarily mean it was a rational decision.
"I think it's quite a good example of where politicians find themselves in difficult positions. I do not envy Jack Straw his decision.
"There was in my view no rational reason for it in terms of the way in which the Parole Board has been asked to deal with release..."
He said the public trust in release decisions could be undermined because of the "political element" currently involved.
"I do think the public might well have started to think 'Is it wise for there to be a political element in the decision-making process because it may distrust the rationality of the decision."
Had Biggs's lawyers challenged the ruling by judicial review, Sir David said, they would probably have been successful.
In his submission to the Ministry of Justice on reforms to the Parole Board's functions, he called for wide-ranging measures to "depoliticise" early release.
He added: "There is a feeling that we all know that when the Parole Board makes decisions which Noms (the National Offender Management Service) does not particularly approve of, then Noms doesn't accept them."
Sir David said the Justice Secretary should also be stripped of his power to decide when prisoners can be moved from closed to open prisons. Such decisions affect when prisoners are likely to be released.
Successive Home Secretaries refused to transfer Moors Murderer Myra Hindley to an open prison before her death in 2002 - despite her pleas.
Sir David said: "We consider there is no proper justification for the present power that we have simply to advise on the transfer of prisoners from closed to open."
He warned of the "terrible" delays in Parole Board cases because of "overload" and accused ministers of failing to allow for the implications of prisoners given Indeterminate sentences for Public Protection (IPPs).
A backlog of around 2,000 cases means some prisoners are waiting up to 18 months after their potential release date before their cases come before a panel.
"We are in such a serious state of overload at the moment that deferral rates are something that we have to try and reduce significantly," Sir David said.
"The Government simply failed to factor in the consequences of putting in another new tranche of indefinite sentence prisoners that do have to be dealt with both by the Prison Service and the Parole Board."
To give the Parole Board more independence, its funding should be included within the grant given to the Courts Service, he said.
Closer links with the courts would give the board better access to judges it needs to chair boards.
The Parole Board should also have the power to compel witnesses and prison officers to attend Parole Board hearings, he said.Reuse content