The fear is that the public will be put at greater risk

The warning by the Parole Board highlights the difficulty it faces when deciding whether or not it is safe to free the hundreds of prisoners whose cases are assessed each year.

Its priority, and its legal duty, is to protect the public by ensuring that inmates thought likely to reoffend remain in prison. To perform this task it has so far been able to use a wider range of material - much of which would not be admissible in a normal court.

The reason for this is that unlike a court, where prosecutors have to provide proof about things that have already happened, Parole panels must assess the risk of something happening in the future.

Future risk is, of course, impossible to prove definitively, so panels regularly place weight upon hearsay testimony, which often comes from other prisoners.

These prisoners are generally unwilling to make their claims publicly - as they would have to do if such evidence was to be accepted in court.

What the Parole Board is now concerned about is the growing pressure for it to adopt a more court-based approach to its hearings.

Such a change would give prisoners - and crucially their lawyers - greater rights to challenge the material used against them when release bids are assessed.

It would be seen by some as a welcome improvement in the treatment of prisoners.

Others, however, will worry that ultimately the public will be placed at greater risk, as some offenders who would otherwise stay in jail are freed instead.

Striking the right balance will not be easy.