By Lord Marks

Statistics don't tell the whole story. But they do tell us about trends – and the trends for violence in Britain's prisons could hardly be worse. The final annual report from Nick Hardwick, the outgoing chief inspector of prisons, painted a bleak picture a year ago:

“You were more likely to die in prison than five years ago. More prisoners were murdered, killed themselves, self-harmed and were victims of assaults than five years ago. There were more serious assaults and the number of assaults and serious assaults against staff also rose.”

Then in April we had a devastating report of an unannounced inspection of one of Britain’s larger Victorian prisons, Wormwood Scrubs, which was built by prisoners on Millbank Gaol between 1875 and 1891. It holds about 1,250 prisoners in west London, just a short distance from the smart homes of Notting Hill. The inspectors reported that safety at the prison had deteriorated since their last inspection in May 2014, that prisoners felt unsafe, assaults on prisoners and staff had doubled, prisoners were too frightened to leave their cells and felt inadequately supported by staff.  Most depressing of all was the failure to remedy the faults found at the last inspection. Of 84 recommendations, only 17 had been achieved in full, 16 had been partially achieved and 51 had not even been partially achieved.

Then last week the Ministry of Justice published the most recent figures for deaths in custody and violence in prisons. There were substantial increases in every category, averaging about 25%. There had been 100 suicides in custody, up from 79; assaults on staff was up by 36% to 4,963; there were 32,313 reported incidents of self-harm (that's 377 per 1,000 prisoners) – an increase of 25%. These figures are truly shocking and shame our country.

I believe Michael Gove and David Cameron are sincere in their commitment to prison reform. They have announced an ambitious programme of building new prisons to replace many of the outdated, squalid and crumbling institutions that so disfigure our penal landscape.

But building new prisons will not meet urgent short term needs. Nor will it bring long term improvement unless we also reduce prison numbers and make prisons work as places for rehabilitation.

We know what causes violence in our prisons: overcrowding, under-staffing, low staff morale, prisoners locked away in cells for too long, a lack of meaningful work, insufficient education, squalid conditions, drugs, including legal highs, and mental health issues.

These same factors cause our sky-high reoffending rates – about 45% within a year of release overall, or about 58% for those sentenced for less than a year. Prison doesn't work and short sentences work worst.

We send far too many offenders to prison.  We imprison too many drug offenders rather than treating their addiction.  We provide too little education in prison to improve life chances on release.

Dame Sally Coates’ review promises to “put education at the heart of the prison system” – and not before time. However, to reduce violence now, we need urgent action.

Sentences should be reduced to cut prisoner numbers. We should release more prisoners early, with greater supervision on release. All those serving indeterminate sentences who have served their tariff should now go free in the absence of a provable and significant risk to public safety. We should hire more prison staff now, to relieve under-staffing. We should cap the number of hours prisoners can spend locked away in their cells. We should increase work opportunities.

Reducing prison numbers will save money – nearly £40,000 per prisoner per year – but, in the short term, hiring more staff will cost money.

Securing resources from the Treasury for the MoJ’s unprotected budget is difficult. But the Treasury must spend to save.  The estimated annual cost of reoffending is between £9.5 – £13 billion. Cutting reoffending and reducing prison numbers would reduce the cost of prisons and of criminal justice. But the long term savings in benefits, housing and social services would also be massive.

Today I will be asking the government in the House of Lords what plans they have to improve prison safety in the short term, given the crisis of violence in our prisons. If it recognises the urgency and can be persuaded to spend now to save later, the long term savings will be substantial – in money terms and the social and human costs of crime.

Lord Marks is the Lib Dem principal spokesperson for justice in the Lords.

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