More than 2,600 prison staff face deportation under new visa rules which “could collapse” the system, unions have warned.
Confidential government data shows one in 25 are foreign nationals working on right-to-work visas.
Under Home Office rules introduced in July, anyone earning below the new £41,700 salary threshold risks being booted out when they expire, ITV News revealed.
A source within His Majesty’s Prison and Probation Service told the broadcaster around 2,200 of those affected are prison officers, with the remaining 400 in support roles.
Starting salaries for prison officers range from £33,750 to £44,500 – with only those working the longest hours inside London on the higher end.
It comes as London mayor Sir Sadiq Khan urged the Government to pause the introduction of new visa rules that could result in between 200 and 300 Transport for London staff being deported.
The Prison Service is already under strain after two prisoners were freed in error from HMP Wandsworth following the high-profile blunder of releasing Hadush Kebatu, the now-deported migrant at the heart of protests in Epping, Essex.
Some 91 inmates were mistakenly freed between April 1 and October 31 this year.
Justice Secretary David Lammy confirmed three prisoners are at large.
There have also been repeated warnings of prisons being at full capacity, underfunding and mounting operational pressure.
Mark Fairhurst, national chair of the Prison Officers’ Association, said the number of staff on right-to-work visas is “considerably higher” than first thought.
Mr Fairhurst added: “We simply cannot afford to lose that many frontline staff and if the government does not exempt the prison service from the new salary thresholds many prisons will not be able to function and we will totally destabilise the prison estate.”
The Prison Governors’ Association warned that the loss of these staff would “leave a gap that cannot easily be filled” and that governors cannot run “safe stable prisons without the right number of officers”.
A spokesman said: “Forcing these officers out in large numbers would be a serious blow. Their departure will leave a gap that cannot be easily filled – and lack of experience is already a key factor in why conditions in some prisons are falling short.
“It would be short-sighted and damaging for the government to allow this situation to unfold. We need solutions that protect the frontline, not policies that weaken it.”
The Government told ITV News: “Working in prison is an extraordinary job and we are always looking for people who want to help keep the public safe to join.
“We are clear that net migration as a whole must come down after quadrupling in recent years as we replace Britain’s failed immigration system with one that is controlled, selective and fair.
“We will of course provide support to those who are affected by these changes, and anyone with a Skilled Worker visa can be considered for an extension.”
