Internal Home Office memoranda seen by the Independent on Sunday reveal that members of the board believe that Mr Clarke is threatening to 'dilute the independence' of the quasi-judicial body, which has become one of the most powerful institutions in the criminal justice system.
When challenged, the Home Office last week strongly defended its new policy, saying there was no political interference and that the public and prisoners had a right to expect consistent decision-making on when criminals should be released.
The passion on both sides is a sign that membership of the board - currently run by representatives of the 'great and the good' - has deep political resonance in the present highly charged debate about crime. Since October, the board has had the power to decide when offenders serving
between four and seven years and 'discretionary lifers' - criminals given life for crimes such as rape and grievous bodily harm - should be released. At stake is who should be in charge and, by extension, what the grounds for releasing the various offenders should be.
The row began three weeks ago when the Home Office told the 85 judges, psychiatrists, criminologists and lay members of the board, who take time off from their regular work to hear prisoners' cases every three weeks, that it wanted to appoint a small group of full-time professionals.
Under Mr Clarke's plan, membership of the board will probably be cut to about 50 and nearly every prisoner seeking parole would find one of the new group of five full-timers would be on the three- to five-member panel hearing his case.
Mr Clarke ordered the change after a Home Office management review decided that full-time board members would bring consistency to decision- making. Board members are appalled. 'We're talking about political placemen who would have their salaries paid by the Government and would find it very difficult to withstand political pressure,' said one leading member.
An internal board memorandum said that there was no evidence of inconsistencies in past rulings and demanded to know where the allegation of capriciousness had come from. If full-time members were appointed they would have to consider between 30 and 60 cases a week. The 'weight of documents' they would have to read would be on such a scale that they would inevitably be forced to reach arbitrary decisions. The pressure of work would 'soon turn them into ciphers'.
Meanwhile, the strength of the present system, that it could call on people from a wide variety of backgrounds to judge whether it was safe to release a criminal, would be lost. Judges, probation officers and other senior officials in the criminal justice system would not give up their careers to work full-time on the board. 'Professional members could be seen as
diluting the independence' of the board, the memorandum concluded.
But Home Office sources replied that, far from boosting Mr Clarke's power, the new system limited government involvement in judicial decisions and brought openness to the previously murky parole procedures.
Until last year the Parole Board was merely advisory, they said. Its members - who in any case have always been appointed by the Home Secretary - could recommend that a prisoner be released, but it was up to the Home Office to decide whether this was the right course.
Now the board was being given the power to decide when most prisoners should be released without reference to the Home Secretary, and as a result the number of Whitehall civil servants who could intervene on parole decisions was being cut from 90 to five.
Full-time board members would be 'well-qualified and independent people', probably with experience of the criminal justice system, they added, and there was no reason why high-fliers would not have a career break and take the job for a few years.
Canada has full-time officers deciding on parole without complaint from prisoners' rights and civil liberties groups, said one source. 'We're not trying to pack anything. We just want a balanced approach. At present we have 85 people spread all over the country and it is hard to develop consistent procedures.'