A record number of prisoners died last year, according to figures released by the Ministry of Justice. There were 68% more prisoner deaths than 10 years ago with 257 people dying behind bars. The number of suicides has risen rapidly since 2006; 119 of the deaths last year were self-inflicted.

The Ministry of Justice has launched an inquiry to investigate mental health in prisons following the highest number of suicides recorded since records began in 1978.

The ageing jail population has also contributed to the sharp rise in prison deaths. 146 inmates died from natural causes last year, a 76% increase since 2006.

The 'Safety in Custody' report also recorded the highest number of self-harm, 37,784, and assault incidents, 25,049 in 10 years. There were 6,430 assaults on prison staff, a 40% increase on the previous year.

A spokesperson for the Prison Reform Trust said: "Dying in prison is the worst thing that can happen. The increase in natural and self-inflicted deaths since 2006 have their roots in an over reliance on custody and overcrowding, that have caused declining standards of safety and decency across the prison estate."

Frances Crook, the Chief Executive of the Howard League for penal reform, said: "Cutting staff and prison budgets while allowing the number of people behind bars to grow unchecked has created a toxic mix of violence, death and human misery."

She stressed that the first necessary step was to reduce the number of prisoners. This measure will "save lives and prevent more people being swept away into deeper currents of crime and despair."

Research published by the Howard League last November showed that the increase in prison suicides had coincided with overcrowding as well as cuts to staffing and budgets.

Justice secretary Elizabeth Truss said: "I have taken immediate action to stabilise the estate by tackling the drugs, drones and phones that undermine security."

She added: "We are also investing £100m annually to boost the frontline by 2,500 officers. These are longstanding issues that will not be resolved in weeks or months but our wholescale reforms will lay the groundwork to transform our prisons, reduce reoffending and make our communities safer."

Liz Truss
Justice Secretary Liz Truss said immediate action was being taken Daniel Leal-Olivas/ Getty Images