By Innes Bowen
Producer, BBC Radio 4's Hecklers
One of the advantages of quitting politics is that you get a chance to say what you really think.
When Mark Oaten was the Liberal Democrats' home affairs spokesman his every utterance was pored over for signs his party was going "soft" on crime.
Mark Oaten is quitting politics at the next general election
Even a relatively modest proposal, such as sending young offenders on driving courses, was seized on by his political opponents, who caricatured it as "go-karting for yobs".
It is not hard to imagine, then, the reaction if he had suggested abolishing all prisons.
The Winchester MP desperately wanted to say that all prisons should be demolished and replaced with education and training centres, mental health facilities and drug rehabilitation units.
But his Lib Dem colleagues would never allow him to air this radical view in public.
"It was clear to me that prison wasn't working," says Mr Oaten.
"But I would have been crucified as a front line politician for saying this in public and the party would have tumbled in the opinion polls."
Mr Oaten was forced to quit the frontbench last year after revelations about his private life.
Now that he has decided not to seek re-election as an MP, he is taking advantage of the freedom to express his views.
"Prison is not fit for purpose and it's beyond reform. We need to abolish it and replace it with more workable alternatives," he tells BBC Radio 4's Hecklers, in which provocative views are debated in front of a live audience.
"Prison is meant to do two things: punish and rehabilitate," he argues, but with two thirds of prisoners reconvicted within two years of release, "prison fails on both counts."
The solution, according to Mr Oaten, is to establish new institutions aimed at tackling the root causes of offending.
But critics argue that far from being an ultra-liberal solution to crime, Mr Oaten's proposals would lead to the creation of an authoritarian, Big Brother state in which bureaucrats would have the final say over who is locked up - and for how long.
Is it time to bulldoze all prisons?
The Winchester MP identifies mental health problems, drug addiction and illiteracy as three of the main reasons for criminal behaviour.
Different institutions to tackle different problems should, he suggests, replace the prison system.
In this respect, his proposals are very similar to those outlined by the Conservative leader David Cameron in a Sunday Telegraph article in July.
But critics believe that politicians who put so much faith in the efficacy of rehabilitation schemes are naive.
According to a Home Office study published in 2005 - The impact of corrections on re-offending: a review of "what works" - the vast range of rehabilitation schemes have either been poorly evaluated or shown to make little impact on reconviction rates.
According to Mr Oaten 72% of prisoners have mental health problems.
These people, he argues, should be held in secure therapeutic facilities where they would undergo treatment.
But according to Professor Dirk van Zyl Smith, an expert in penal policy based at Nottingham University, while there is research which shows mental health programmes work for some problems, the vast majority of such schemes have no long-term effect on criminal behaviour.
Personality disorders, such as psychopathy and violent personality disorder, are considered by most psychiatrists to be untreatable.
Mr Oaten believes offenders detained in mental health facilities should only be released when they are no longer considered a threat to society.
David Rose, a journalist who has taken a special interest in criminal justice issues, believes Mr Oaten's plans would result in a highly authoritarian system.
If, as the research seems to indicate, the success rates of psychological treatments is poor, the end result could be large numbers of offenders being detained indefinitely with little chance of release, even if their crimes are relatively minor.
"What Mark Oaten is arguing for is a massive increase in state power with all kinds of new powers for bureaucracies to decide whether people should be released depending on whether they've completed some kind of cognitive behavioural programme," says Mr Rose.
Similar criticisms are also levelled at other aspects of Mr Oaten's vision.
Mr Oaten envisages the drug treatment facilities he proposes attracting plenty of offenders, claiming that currently around 50% of all prisoners have a drug problem.
A Home Office evaluation of the research on drug rehabilitation programmes in prisons shows a reduction in recidivism rates for those who complete drug treatment courses and who receive after care in the community.
However, these differences in reconviction rates gradually fade so that three years after release, reconviction rates are the same for those addicts who go through drug treatment programmes and those who do not.
For those identified as committing crime because of their lack of employability, Mr Oaten would like the government to establish a network of secure education and training centres.
He says: "Thirty seven per cent of prisoners are functionally illiterate. They should be in classrooms learning to read and write or in training and getting skills."
Those sentenced to education and training would be released upon successful completion of their course.
But according to Home Office research: "The emerging evidence on basic skills training in prison suggests that these courses can improve prisoners' skills but the extent to which these can be improved sufficiently to have a positive impact on employment prospects by prison training alone is still in doubt."
Mr Oaten casts doubt on the validity of current research findings in relation to rehabilitation programmes.
"These are evaluations of schemes which have carried out in prisons.
"That's a crucial difference between what I'm arguing for and what's going on now. Creating new institutions is the key thing. What I'm advocating has never really been tried."
Hear Mark Oaten MP argue that "we should abolish prison" on Hecklers, BBC Radio 4, 2000 BST, Wednesday 8 August. Repeated at 2215 BST on Saturday 11 August.