A high-security prison labelled as “struggling” in its last inspection has had eight of its prison officers arrested on suspicion of corruption.

HMP Swaleside on Sheppey, which holds men convicted of serious offences and those who pose a high risk to the public, saw seven of its officers arrested last month, with another held in May, it has emerged.

A spokesman for the Ministry of Justice’s counter-corruption unit, which looks for wrongdoing at prisons and among probation services, said: “It would be inappropriate to comment on a live police investigation.”

A spokesman for Kent Police said: “On Friday, June 14, Kent Police arrested seven people in Swale on suspicion of misconduct in a public office.

“Officers previously arrested another person in connection with the investigation on Saturday, May 18. All those arrested have since been released on bail until various dates in September.”

The prison, which has been described as having “chronic” difficulties in recruiting officers, can hold up to 839 inmates with more more than 40% of prisoners serving lengthy sentences of more than 10 years and 43% serving indeterminate sentences, mostly life, while one unit is for men convicted of sexual offences.

In a report by His Majesty’s Inspectorate of Prisons last September it stated that levels of violence were high at the institution and drugs too easy to obtain.

At the inspection, the presence of many temporary staff from other prisons was noted.

Fourteen prisoners had died at Swaleside in the previous two years, including seven who had taken their own lives.

Inspectors said ongoing weaknesses at the jail included inconsistent support for prisoners at risk, a failure by some night staff to carry anti-ligature knives, slow responses to cell bells, and inadequate reviews of recommendations from coroners and the Prisons and Probation Ombudsman (PPO).

Speaking at the time of the inspection Charlie Taylor, HM chief inspector of prisons, said: “This was our sixth visit to Swaleside since 2016.

“During that time, we have repeatedly raised significant concerns about the prison.

“I therefore decided to announce this inspection six months in advance to give leaders the opportunity to use our inspection as a focus for improvement. Our findings suggest that they grasped that opportunity.

“Outcomes in all four of our healthy prison areas remain concerning, but the governor has shown commendable commitment to the prison and has evidenced an energy and application that has helped keep it remarkably stable despite all the challenges.”

In May as many as 25 prison officers were left needing hospital treatment after a special staff curry was “spiked” by inmates in what the Criminal Justice Workers Union (CJWU) described as a “mass poisoning of staff”.