Self-harm incidents in Littlehey Prison hit their highest level on record in 2018, new figures show.
It follows a violent trend across England and Wales's prisons, where deaths, assaults and self-harm incidents were all at record levels last year.
The prisons minister, Rory Stewart, said figures were "unacceptably high", and warned that the effort required to return long-term stability to the prison estate should not be underestimated.
In Littlehey Prison, 534 self-harm cases were recorded in 2018, with 38 inmates referred to hospital.
This is up from 334 during the previous year and is the highest figure since incidents started being recorded in 2004.
In 2013, there were 194 incidents of self-harm recorded, meaning a 175 per cent increase in five years.
The numbers also reveal that there were 84 assaults in Littlehey in 2018, a 49 per cent drop on 2013.
In total, 21 were defined as serious, including sexual assaults and those where victims required hospital in-patient treatment.
Across England and Wales, 325 deaths were recorded in prisons in 2018, up from 295 the previous year.
In Littlehey, which is in Perry, seven prisoners died in 2018.
Frances Crook, chief executive of the Howard League for Penal Reform, said: "These figures reveal the sheer scale of the challenge to transform a prison system that has been overburdened and under-resourced for years. Change is happening, but it is like trying to turn around an oil tanker.
"I welcome the Government's efforts to reduce violence, including recruiting more staff to increase numbers and refresh the workforce, but fundamental reform is being stymied by the lack of parliamentary time available for legislation.
"I believe the will is there among ministers to make prisons safe and to reduce their unnecessary use, but in the end, lives can only be saved and violence reduced if the nettle of reform is grasped."
The prisons minister, Rory Stewart, said: "Violence and self-harm in prisons remains unacceptably high, but I'm pleased at these early signs that we are making progress.
"It's particularly encouraging to see a quarterly drop in violence, the first in two years. Our dedicated prison staff deserve enormous credit and I want to thank them all for their tireless work.
"There is still much to do, however, and no one should underestimate the effort required to return long-term stability to the prison estate."
Across prisons in England and Wales, more than 34,000 assaults were recorded in 2018, an increase of 16 per cent on the previous year.
Self-harm also increased by 25 per cent, with nearly 56,000 cases in 2018.