The number of prison officers in Styal Prison has increased significantly over the past year, as the establishment tackles rising levels of assault and self-harm.

But unions have warned of high turnover rates among prison staff across the country, with inexperienced officers facing more violence and drug use among prisoners.

The government has hired more than 3,000 prison officers since 2016, following a six-year period during which the prison service lost nearly a third of its workforce.

Newly-released figures from the Ministry of Justice show that there were 17 more officers in Styal Prison in March this year than a year previously - an increase of 10 per cent. there are now 188 prison officers working in Styal Prison.

Glyn Travis, the assistant general secretary of the Prison Officers’ Association, said the high turnover of staff in prisons was a cause for concern.

He said: “The biggest problem is that a lot of establishments have more than 50 per cent of staff who have less than two years’ service in prisons. The attrition rate, for people who leave the service in the first 12 months, is about 16 per cent - that’s a massive increase since 2010, when it was around two per cent.

“In prisons, there are serious acts of violence every day on staff and on other prisoners. The NHS have said that they have concerns for nurses in prisons being in contact with fumes from drugs - prison officers are in this environment every day.

“People are coming into the job and saying this isn’t for me. The risk of life-changing or serious injuries every day is too high.”

The justice secretary, David Gauke, said that 3,111 prison officers were recruited between October 2016 and March 2018, surpassing a government pledge to recruit 2,500 prison officers by the end of this year.

He said: “Going beyond this important milestone so early is a real achievement. It means the vast majority of these prison officers will be working on the landings by the summer, and all of them will be in place by the end of the year. The recruitment drive will continue until we reach required levels across the prison estate, with the same urgency that has secured this remarkable influx of new staff.”

Figures released last month showed that there were 134 assaults in Styal last year, more than triple the level in 2012. Of those assaults, 53 were on staff. Cases of self-harm had also more than doubled over five years.

The prison was also found to be overcrowded, with 463 prisoners placed into cells designed for just 471.