HMP Millsike: £400m 'super prison' still operating hundreds of places below overall capacity

HMP Millsike, on the edge of the East Riding of Yorkshire, opened in March last year to a cost of £400m.

Britain’s newest “super prison” near York is still operating at hundreds of prisoners below its full capacity more than a year after opening, despite the early release controversy rumbling on.

HMP Millsike, on the edge of the East Riding of Yorkshire, opened in March last year to a cost of £400m.

When fully operational it will hold 1,468 prisoners, however at the moment it is restricted to a capacity of 1,158.

The latest Ministry of Justice figures for July show that the prison held 1,124 inmates, 344 below the total it will hold when it eventually ramps up.

It is normal for prisons to slowly increase prisoner numbers after opening, although experts say this usually takes between six months and a year.

HMP Millsike was the first major opening by the Labour government, as it has pledged to create 14,000 extra prison places by 2031.

The category C jail has been designed to cut crime, with 24 workshops and training facilities aimed at getting offenders back into work and away from crime when they are released.

However, the prison - run by private contractor Mitie - has had a bumpy start since opening in March 2025.

Volunteers appointed to monitor conditions at the prison had said they only felt safe to visit in pairs.

They also highlighted poor security, with doors and gates left open, rampant drug use and “frequent reports of batons being drawn”.

The Independent Monitoring Board at HMP Millsike wrote to then-Prisons Minister Lord Timpson in December to raise concerns over the “safety and security” of the site.

Ms Pariser has now been replaced by Sarah Mallender, director of Heathrow Immigration Removal Centre.

They said: “Millsike has been struggling to staff the prison. They have reached the point where they have got all the staff they can recruit to safely operate at a reduced number of spaces but they are struggling to get above that.

“They are experiencing what most prisons are facing. We are recruiting people, training them, then they are leaving. It is a bit like a bath where the taps are on full but you have the plug out, so you are constantly struggling to keep staff levels up.”

The area’s Tory MP Charlie Dewhirst, of Bridlington and the Wolds, told The Yorkshire Post: “The last Conservative government built over 14,000 new prison places and HMP Millsike in my constituency, approved and started by the Conservatives, is a great example of that, providing extra capacity for almost 1,500 criminals.

“Although finished under Labour – who admitted they’ve not approved or planned a single new prison themselves – it is unbelievable they didn’t bother to recruit enough officers to staff Millsike, leaving nearly 350 cells sat empty.

“It’s not just here, there are 1,100 fewer prison officers under Labour, and HMP Millsike is just one of Labour’s half empty prisons – thousands of places across the country left empty because of uninstalled smoke detectors, other unfinished repairs or lack of staff.”

The revelations come with new Prime Minister Andy Burnham under pressure to find ways to exempt more people from the early release scheme, which is designed to cope with prison overcrowding.

However, Mr Burnham is trying to find a way to prevent the killers of Pc Andrew Harper from being released early.

A Ministry of Justice spokesperson said: “We are working at pace to bring every available prison place online – and have always been clear that 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 imprisonment for public protection sentences.”

A Mitie spokesperson added: “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.”