Plans for 20,000 additional prison places by the mid 2020s are not expected to be completed until 2030 due to planning delays.
The £4bn programme has been hit by further problems this summer, a Whitehall source said, which means the new cells will not be available to head off the current capacity crisis.
The disclosure comes as figures published last Friday showed the prison population was 87,685, close to the “usable operational capacity” of 88,314 and up 7% in a year.
The situation is exacerbated by a record backlog in the courts leading to a 50-year high in the number of people on remand.
The plans for the new prison places were signed off by ministers in 2020. Two prisons have opened so far and one is under construction.
But it emerged in June that three of the new super prisons – in Lancashire, Leicestershire and Buckinghamshire – will not open before 2027 at the earliest because of planning appeals.
A senior Ministry of Justice (MoJ) official told a conference that problems had been compounded by badgers which cannot be moved from their setts between July and November.
Antonia Romeo, the most senior civil servant at the MoJ, said in a letter in July that 3,400 of the additional places in England and Wales had been delivered so far. She added that by the end of May 2025, the total will have risen to about 8,200.
An insider confirmed last week that the target of opening all six prisons by 2027 was no longer possible and said they hoped they would be open by “the end of the decade”.
Sir Bob Neill, the Tory chair of parliament’s justice select committee, said that the development raises questions about the lack of “joined up government” when it comes to prison numbers.
“There must be a rethink so that the Home Office stops calling for longer sentences and the Ministry of Justice anticipates these problems. The government cannot keep trying to squeeze a quart into a pint pot,” he said.
Pia Sinha, the chief executive of the Prison Reform Trust, said the development should jolt the government into reducing the number of prisoners.
“The Prison Service will not be able to build its way out of the capacity crisis it is facing.
“Ministers now have no choice – however politically unpalatable they must now bring forward proposals to urgently reduce demand on the system,” she said.
Shabana Mahmood, the shadow justice secretary, said the prison estate is in crisis because of the government’s failure to provide adequate facilities.
“This is yet another Tory failure of their own making. The prison estate is in crisis because they have failed to deliver the very prison places they have been promising for so many years.”
An MoJ spokesperson said: “Our plan remains to build six new, modern prisons to protect the public and better rehabilitate offenders as part of a programme to create an additional 20,000 places in the biggest estate expansion in over a century.
“We have always been clear that delivery dates are contingent on external matters, including planning permission, but we remain committed to building these prisons as quickly as possible.
“Around 5,500 places have already been delivered and we are due to have around 8,000 in place by May 2025.”
