Nearly 350 cells at Britain’s most expensive new prison sit unused despite the UK facing a severe capacity crisis.
HMP Millsike, a £400m “super-prison” outside York designed to accommodate close to 1,500 prisoners, is currently capped at roughly 1,100 as capacity is phased in to ensure the prison remains safe as it ramps up.
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As of last month, 344 cells remained unoccupied, a capacity that sits idle while the wider prison system buckles under severe overcrowding.
The jail, which welcomed its first inmates in March 2025, was intended to be fully operational within six months to a year, yet its designed capacity of 1,468 has still not been reached.
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The empty cells have taken on political significance after Andy Burnham instructed Justice Secretary Alex Norris to find a mechanism for blocking the early release of two men convicted of killing PC Andrew Harper, who received manslaughter sentences in 2020.
The MoJ has reportedly cautioned the Prime Minister that carving out exceptions for individual offenders would require retaining all prisoners found guilty of the same offence.
Some 470 inmates currently serving manslaughter sentences are due to become eligible for early release from October under the government’s overcrowding reduction scheme.
Millsike’s 344 vacant cells could theoretically house the majority of them.
GB News understands the occupation of new prisons is phased and managed carefully to ensure the prison remains safe, secure and stable as it ramps up.
Staffing is one of the operational factors considered, alongside safety and security.
The People’s Channel also understands that capacity will increase when the MoJ deems it operationally appropriate.
The prison boasts some of the most advanced cells in the country, fitted with reinforced windows without bars and private shower and toilet facilities.
Its rehabilitation offering, funded as part of the £400m build, alongside a £33m annual operating contract held by Mitie, includes allotments, three multi-use sports pitches with outdoor gym equipment, and 16 workshops capable of training up to 500 inmates simultaneously in trades such as bricklaying, carpentry and barbering.
Yet the facility’s early months have been far from smooth.
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In January, the Independent Monitoring Board raised “serious concerns” about high assault rates, staff leaving doors and gates unsecured, and the ready availability of drugs.
Elsewhere in Britain, around 1,800 cells sit empty due to “uninstalled fire safety systems”.
Speaking to GB News, broadcaster Tim Vincent said the figure is “staggering”, arguing: “Thousands of prison cells are lying empty even though the Government is releasing criminals early to tackle overcrowding.”
He added: “1,800 places behind bars cannot be filled because of a pledge to install fire safety systems. It’s staggering really, isn’t it?”
Prisons across Britain are suffering from a staff recruitment crisis, according to reports.
A senior prison source compared the staffing situation to “a bath where the taps are on full, but you have the plug out, so you are constantly struggling to keep staff levels up,” when speaking to The Telegraph.
Across the older estate, including Victorian-era institutions, more than 4,000 places remain closed due to maintenance requirements, fire safety upgrades or health hazards.
Governors report that even refurbished wings cannot reopen without sufficient personnel.
Ian Acheson, a former governor and government adviser on prison extremism, urged Mr Burnham to establish a “national emergency taskforce” with the authority to override the MoJ and unlock additional capacity.
He said: “I am convinced that additional capacity could be found to stop repeat knife carriers and domestic abusers being released early. But it takes political will, urgency, imagination and some risk-taking.”
An MoJ spokesman told GB News: “This government inherited a prison capacity crisis after prison places increased by just 500 places in 14 years. We are pulling every lever possible to fix that crisis and are building 14,000 new places with 3,200 already delivered.
“We are working at pace to bring every available prison place online – and have always been clear new prisons require a ramp up period to ensure they remain safe, secure and protect the public.
“We are also exploring how we can go further to increase capacity, including faster deportation of foreign criminals, better use of the women’s estate and reviewing the unjust IPP sentences.”
A Mitie spokesman said: “HMP Millsike continues to operate in line with the ramp up plans agreed with the MoJ, with staffing and recruitment aligned to the prison’s phased population build-up.
“We remain focused on maintaining a safe, secure and supportive environment for prisoners and colleagues.”
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