Every jail in England and Wales will be completely full within six weeks, prison chiefs warn.
There are only 900 places left and the system will not have room for a single extra inmate by July, they say.
Andrea Albutt, president of the Prison Governors Association, is calling for the Government to “be brave” and let lags out early.
There are currently 85,190 prisoners in England and Wales – 5,000 more than this time last year.
It is the first time inmate numbers have topped 85,000 in six years. Prisoners are already being kept in police cells overnight when local jails are full.
Ms Albutt – who has headed jails in Bristol and Swansea, and HMP Low Newton, County Durham, which has hosted notorious inmates including Rose West – said even open prisons with the most space are 97% full.
And she warned governors will take legal action if they are forced to breach strict capacity limits amid this “perfect storm”. Ms Albutt said: “Our prisons are full and the prison building programme cannot keep pace with the increase in the prison population.
“Short-termism, party politics and constant changes of Secretaries of State leave a system feeling like a political football, with no evidence of sustained improvement”. Factors that have fuelled the “major capacity problem” in jails incude more people on remand due to Covid clogs, barristers’ strikes and an increase in convictions, a Ministry of Justice insider revealed. The source added: “The prison system is running out of space and there are no quick fixes.”
The MoJ forecasts inmate numbers will hit 94,400 by March 2025. A drive to build 20,000 extra places, including six new jails, has been hit by planning permission delays at three sites.
The MoJ said: “We’re building six new prisons and creating an additional 20,000 places to deliver the biggest prison expansion in a century.
“We’re also taking action to accelerate additional capacity in the immediate term, including rolling out hundreds of rapid deployment cells – with the first already in place at HMP Norwich.”