Plans for two new prisons in South Wales and Yorkshire have been revealed as part of a £1.3bn government pledge to create 10,000 modern prison places by 2020.
Sites in Port Talbot and Full Sutton, near York, have been earmarked, while two existing jails in Kent and Wigan will also be redeveloped.
Justice Secretary Liz Truss said modern jails would help cut reoffending.
But Peter Dawson, of the Prison Reform Trust, said "closing prisons, not opening them" was a better solution.
A final decision on the two new prisons depends on planning approval and "value for money", the government said.
The two jails being redeveloped - HMP and Young Offender Institution (YOI) in Rochester in Kent and HMP and YOI Hindley in Wigan - will both be shut while extensive rebuilding work takes place.
The construction programme will be offset by the closure of a number of older prisons, the details of which have yet to be confirmed.
Ms Truss has vowed to overhaul the system, improve the estate and recruit more officers.
"Outdated prisons, with dark corridors and cramped conditions, will not help offenders turn their back on crime - nor do they provide our professional and dedicated prison officers with the right tools or environment to do their job effectively," she said.
But Mr Dawson, who supports an overhaul of the prison system, criticised the plans, saying: "This massive investment in new prisons is not matched by a credible plan to reduce our reckless overuse of prison in the first place."
Shadow justice secretary Richard Burgon said: "Simply replacing one prison with another prison doesn't deal with the overcrowding crisis."
Last month the UK's newest prison, HMP Berwyn in north Wales, opened its doors to more than 2,000 inmates.
The £250m jail, Britain's biggest, contains a health and wellbeing centre, an education block, a sports hall and a multi-faith area.
Planning applications are under way to redevelop sites at the former HMP Wellingborough, Northamptonshire, and HMP and YOI Glen Parva, in Leicestershire.
Building work has begun on a new block at HMP Stocken in Rutland.
The proposed new-builds at Port Talbot and Full Sutton will create up to 2,000 construction and manufacturing jobs, the government said.
Source: BBC News