Government faces huge payouts after court rules detention of sex offender is 'unlawful'

The High Court said the Ministry of Justice was treating convicts of 'indefinite' sentences illegally by failing to consider them for release as soon as their minimum term is over.

The ruling came in a case brought by two inmates serving indeterminate sentences with recommended minimum terms or 'tariff' periods imposed on them for the protection of the public.

One of the inmates is sex offender David Walker, presently serving a minimum 18 months for indecent assault. The test case means hundreds of inmates could be eligible for compensation.

Walker's legal team claimed he was being subjected to arbitrary detention in breach of his human rights as he was to be forced to stay in prison indefinitely until a parole board panel gave clearance for his release.

Walker argued the lack of parole courses which must be completed before a release hearing meant it would be difficult for him to be freed at all.

The decision means the Government will be forced to plough cash into prison treatment programmes. Lord Justice Laws, sitting with Mr Justice Mitting, said: "His detention cannot in reason be justified. It is therefore unlawful."

Campaigners claim "indeterminate sentences for public protection", known as IPPs, are contributing to the prison overcrowding crisis.

Already sex offenders are living in the community without proper checks because of government funding shortfalls.

The rising number of people registered as violent criminals or sex attackers is overwhelming supervising bodies, a report commissioned by the Home Office says.

The study from De Montfort University highlighted a severe shortage of approved accommodation for offenders, funding shortfalls to supervise violent people released from jail, a lack of treatment programmes, and the rising number of individuals on the sex offenders' register.

It says: "There were grave concerns resources were not increasing as the registration list does."

Responsibility for keeping offenders under watch falls to the Mullet-Agency Public Protection Arrangements (Mapa).

But those on the frontline expected to carry out the monitoring - the police, probation officers and social workers - are becoming increasingly strained.

According to The Times, the report states: "Participants expressed concern about increases in workload which they felt would be an inevitable consequence of any public disclosure.

"Of particular concern was the potential impact on police resources and the diversion that issues such as offender 'outing' and subsequent rapid rapid relocation of offenders to place of safety, and other related public disorder might mean for the supervision of cases."

The study will come as a fresh blow to the government which only earlier this year admitted that police had lost track of 322 registered sex offenders across Britain.

It will also increase pressure on the government to allow public access to known sex offenders living in the community.

The Home Office had to monitor 47,653 offenders in England and Wales between 2005 to 2006.

The numbers under supervision have risen after new offences for outraging public decency, theft, burglary with intent, child abduction and harassment were added to the watch list.