Labour has pledged to deliver 14,000 new prison places to tackle the overcrowding crisis if it gets into government.
The party has announced plans to unblock the planning system in order to expand the prison estate and ease capacity.
Prisoners have been let out of jail early in recent months as part of emergency measures to tackle a chronic shortage of spaces.
Overcrowding has also resulted in offenders being held in police cells and officers being asked to consider making fewer arrests.
Labour said the prison estate is “bursting at the seams” due to inaction and mismanagement by the Conservatives.
The Tories previously promised to deliver 20,000 new prison places by the mid 2020s but only 6,000 have been created so far.
Labour said it will deliver the remaining 14,000 if it gets into government.
Shadow justice secretary Shabana Mahmood said: “The crisis in our prisons is a powder keg waiting to explode. Worse still, we never had to get to this point.
“The dangerous overcrowding of our prisons was foreseeable and avoidable, but this government has not had the will or courage to act.”
She added: “We will build the prison places they promised but never delivered and we will drive down reoffending.”
It is understood the new spaces will be created by a mix of expanding the size of current prisons and building new ones.
Labour plans to designate prisons as sites of national importance, placing the power to approve a planning decision in ministers’ hands, in order to speed up the process.
In 2019, then prime minister Boris Johnson pledged to create an additional 10,000 prison spaces by 2025. This was on top of the 10,000 places his predecessor Theresa May had promised to build in 2016.
