Public protection experts have criticised two psychologists who backed the release of the serial sex attacker John Worboys and subsequently stated that his failure to acknowledge his crimes make him a low risk to women if freed.

In a letter to the Psychologist magazine, they suggest that Worboys’ lack of empathy for his victims means he is less likely to offend again. This conflicts with the views of most experts, who believe that offenders must address their past behaviour if they are to be successfully rehabilitated.

The two independent experts, known only as P12 and P1 in court papers, were instructed by Worboys’ defence team. They were among four psychologists whose opinions helped convince the parole board that he should be released, despite opposition from some prison and probation officials. Their controversial opinions are likely to prompt questions about what weight should be given to expert witnesses employed by defence lawyers seeking their clients’ release.

In their letter, the psychologists claim that Worboys’ “denial of the offences for many years, his apparent failure to confess to all his crimes, suspicions about his level of remorse and victim empathy – are the very issues for which there is robust evidence regarding their lack of association to risk”.

They quote a 2015 study of 7,000 convicted UK sex offenders which found that “those who took full responsibility for their offence sexually reoffended at a significantly higher rate than those who took partial or no responsibility for their offence. “We now know that these post-hoc offence rationalisations are driven by shame, a functional response to wrongdoing, often held by those individuals with stronger social bonds.”

But the claim has been met with scepticism from other experts. “To suggest that sex offenders who are repeat abusers and in denial are not necessarily a high risk of causing further harm is highly controversial,” said Harry Fletcher, a probation expert. “Offenders in the prison or probation system who deny they did it or who claim that their victims consented are hard to work with as they do not address their offending behaviour.”

“Denial is consistently used in forensic settings to determine the level of risk,” said Keri Nixon, a consultant forensic psychologist with 16 years’ experience of working in risk assessment. “The extent of the offences committed in this case, the chronicity of offending and the nature of denial all suggest he is a high-risk offender.”

The decision taken by the board in January to release Worboys, more than eight years after he was jailed for 19 sex offences against 12 women in London, provoked a furore. Last month the board was forced to reconsider its decision following a judicial review brought by two of his victims that led to the resignation of its chairman, Nick Hardwick. He was told by David Gauke, the justice secretary, that his position was untenable.

In prison, Worboys maintained his innocence until the earliest date when he was eligible for parole neared. In January 2015 a psychologist noted he continued to maintain his innocence and “there was no reduction in the risk” he posed to the public.

But six months later, as a potential release date loomed, court documents note that Worboys had a sudden change of heart.

A parole board spokesman said: “Psychologists who give evidence are not parole board employees and will either be instructed by Her Majesty’s Prison and Probation Service or the offender.”

A Ministry of Justice spokesman said: “These reports are just one of many pieces of evidence parole board panels, often including members who are themselves experienced and registered psychologists, consider before coming to a decision.”