Ninety prisoners are on the run from Ford Open Prison in West Sussex, the BBC has learned.
Ford and other open prisons have seen a series of high-profile disappearances in recent weeks.
Both Sussex MP Nick Gibb and the Prison Officers Association (POA) have said mistakes are being made because of “constraints” in the prison service.
The Ministry of Justice said immediate and major changes had been ordered to tighten up the system.
Figures issued by Sussex Police said there were currently 90 people missing from Ford with some missing for weeks but others for years.
The prison can take up to 557 inmates and accepts offenders with under two years left to serve.
Quick steps taken
In November, the force found there were a number of people who had absconded whose cases had not been regularly reviewed, and a dedicated team was set up to review each case.
Supt Lawrence Hobbs said the force made “some very quick and positive steps” and had arrested 23 absconders since then. About 23 people disappear from the prison each year.
This week, the force was criticised for waiting four years to tell the public there was a convicted murderer on the loose.
Supt Hobbs said police did not routinely make media appeals to the public when people went missing, but considered each case individually, taking into account the risk.
He said the vast majority were serving jail terms for offences such as fraud, dishonesty and theft, and he added: “We are absolutely confident the risk to the public remains low.