Justice Secretary Liz Truss has condemned "unacceptable" levels of violence in prisons as it emerged attacks on guards have jumped by 99% in less than four years.

The figure was revealed as the Government unveiled its blueprint for what is billed as the biggest overhaul of jails in a generation.

A white paper outlining the reforms said assaults against staff across the estate are the highest on record and continuing to rise.

Comparing the 12 months to June this year with the calendar year 2012, assaults on officers had risen by 99%.

The most recent statistics showed nearly 6,000 attacks on staff in the year to June.

Rising levels of violence have prompted repeated warnings about the state of prisons in England and Wales, with the head of the Prison Officers Association warning jails have been engulfed by a "bloodbath".

On Thursday Ms Truss set out plans aimed at improving safety - including a recruitment drive to add 2,500 new officers and "no-fly zones" to stop drones dropping drugs and other contraband into prison grounds.

In a speech in central London, Ms Truss said levels of violence and self-harm in prisons are "totally unacceptable" and expressed her determination to "turn the tide".

The strategy will also see:

:: A programme offering offenders opportunities that will count towards the completion of a formal apprenticeship on release. Ms Truss said the Government will sign up some of the biggest names on the high street and in industry to commit to taking on former offenders as apprentices for a minimum of 12 months on release

:: Steps to overhaul intelligence gathering

:: Five new community prisons for women

Writing in the white paper, Ms Truss said: "For too long society has failed to look over those high walls and the result has been a catastrophic burden on the taxpayer and far too many lives shattered by crimes.

"This is a blueprint for the biggest overhaul of our prisons in a generation. This is a challenge that will take time and determination to deliver but society can no longer afford to ignore what goes on behind those high walls."

Former justice secretary Ken Clarke branded jails "overcrowded slums" and called for fewer custodial sentences.

He said the Government must tackle the trend to hand out more and tougher jail terms which has developed over the last 20 years.