71 prisoners were released by mistake in the UK last year

More than one prisoner a week was released by mistake in 2016/17, new figures reveal, as violence in prisons surged to new highs.

71 convicted criminals or suspects were accidentally released — the highest number since current records began a decade ago and an increase of 7 on the previous year.

The Ministry of Justice figures released on Thursday also show a record number of attacks on prison staff and high numbers of assaults amid fears of growing violence in the UK’s prisons.

Prisons across England and wales saw 26,643 assaults in the year to March 2017, including a record 7,159 attacks on prison staff — equivalent to almost 20 a day.

Justice Secretary David Lidington said improving safety was his “top priority”.

“These figures reinforce how crucial it is that we make progress as quickly as possible”, he said.

“As the chief inspector of prisons rightly observed in his annual report last week, we cannot achieve successful reform and rehabilitation unless our prisons are safe and secure – and this is something I am committed to achieving.”

Lidington, who’s spent just a month in the post, added:

“I have seen first-hand the challenges our dedicated and hardworking prison staff face. Boosting the frontline is critical to achieving safety and the number of prison officers we are recruiting is rising, with the number of new prison officers joining the service at its highest level since 2010”.

Inmates released due to blunders are not considered to be unlawfully at large, meaning they may not be pursued by authorities.

For those who are kept in custody, rates of self-harm showed an alarming increase of almost 6,000 on the previous year, reaching a record high of 40,414 incidents. The number of suicides dropped slightly to 97, including six women.

Deaths in prison custody totalled 316, also down slightly on the previous year, but the increasing incidents of self-harm and assault will cause alarm.

Campaigners and watchdog groups have repeatedly warned about prison safety amid concerns over staffing levels and conditions.

The Prison Reform Trust told The Independent the latest figures showed that Britain’s prison system is “nowhere near being safe for those who live and work within it”.

The campaign group’s director, Peter Dawson, said that “the appalling loss of life and toll of despair requires something more immediate than the promise of more staff and new prisons”.