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

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

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

Newly-released figures from the Ministry of Justice show there were 58 more officers in Swaleside Prison in March this year than a year previously - an increase of 22%.

It means there are 327 prison officers working at Swaleside.

There were 42 more officers employed in Elmley Prison during the same period, bringing the total to 317.

Figures at Standford Hill increased by seven, putting the total at 88.

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

He said: “The biggest problem we see now is that a lot of establishments have more than 50% 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% – that’s a massive increase since 2010, when it was around 2%. In prisons, there are serious acts of violence every day on staff and on other prisoners.

“The biggest problem we see now is that a lot of establishments have more than 50% of staff who have less than two years’ service in prisons..." - Glyn Travis, Prison Officers’ Association

"The NHS has said that it has 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.”

Justice secretary David Gauke said 3,111 officers were hired between October 2016 and March 2018, beating a government pledge to recruit 2,500 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.

“This will make a real difference to the safety and security of our prisons, ensuring they can fulfil their purpose protecting the public, reducing reoffending and, crucially, rehabilitating offenders.

“But let me be clear - the recruitment drive continues and will continue until we reach required levels across the prison estate, with the same urgency that has secured this remarkable influx of new staff.”

In total, there were nearly 26,000 prison officers employed across 108 government-run prisons in England and Wales in March this year - an increase of 10% on 2017, but still significantly lower than 2010 levels.

Figures released last month showed that there were 305 assaults in Swaleside last year, five times the level in 2012 assaults, 106 on staff.

Cases of self-harm had also risen to more than five times their level of five years previously.

The prison was also overcrowded, with 1,011 prisoners in cells designed for just 1,059.