Major failings in the provision of healthcare at Liverpool prison have been uncovered by a BBC investigation.
Whistleblowers have told BBC News that prisoners have died and others have been injured due to poor care.
Most of the incidents have happened since inspectors said conditions at the jail were the worst they had seen.
Lancashire Care NHS Foundation Trust said it was sorry it had not managed to improve services as much as it had hoped.
For the past three months, healthcare staff at HMP Liverpool have been highlighting ongoing concerns about the treatment of some of the approximately 1,100 prisoners at the jail.
Their decision to speak out, they say, was borne of a sense that senior management at the trust were not listening to concerns and hiding failings from regulators.
In September, HM Inspectorate of Prisons visited Liverpool.
A draft copy of its report, obtained by the BBC, says while there have been some improvements, "there is a lack of support for people with mental health needs, and in-patients have an impoverished regime. There had been failures of leadership and management at all levels."
Just days after the inspectors left, the BBC was informed of the suicide of a patient.
The man, who the BBC is not naming, killed himself in the healthcare unit.
A fortnight later, staff told of the suicide of a second inmate.
"He did not have his secondary screening at the prison, a national requirement," wrote staff in an email to the BBC. "The prison at the moment is so risky."
A month later, a third death. On the day the man died, the BBC was told he had been waiting "nearly 17 hours" to see a prison GP.
Another inmate, we were told, was left with life-changing injuries after staff failed to notice for 12 hours that he had broken his neck despite a medic checking on him.
Darren Harley was convicted of drugs offences and spent 27 months in Liverpool prison before being released in the summer.
During his time inside, he says, he developed toothache but the healthcare regime failed on four separate occasions to provide him with proper medication, forcing him to take drastic action.
"My tooth actually shattered and because of the agony I was in, I ended up having to remove the roots myself. I don't understand how it is taking so long for people to get important medication," he said.
Whistleblowers spoke of regular problems with medication.
'Cockroaches and rats'
On some occasions, potentially life-saving drugs, such as warfarin and insulin, were not available despite being prescribed to prisoners.
At other times, mistakes led to inmates getting double doses of certain drugs.
Lancashire Care NHS Foundation Trust, which has provided healthcare services at the prison for two years, said it inherited some very significant challenges from the previous provider.
It said improvements had been made but the scale of the changes needed and the challenging environment within prisons has limited its ability to address everything.
Rosie Cooper, the Labour MP for West Lancashire, has been campaigning for improvements at the prison for years and is appalled by the continuing failures.
"We expect those prisoners to obey our rules outside of prison, yet inside prison the authorities abandon all rules and regulations and treat prisoners in this way and leave them suffering. I cannot accept that that's right."
As the BBC revealed on Monday, the inspectorate's findings on HMP Liverpool - a local category B/C prison, which also takes people on remand - are damning across the board.
It describes living conditions "as amongst the worst we have seen", with many prisoners living in "squalid" conditions.
"Many cells have broken windows with dangerous jagged glass, broken observation panels, damp, leaks and broken or blocked toilets," says the report.
"There is a significant problem with cockroaches and rats throughout the prison."
The problems are understood to have contributed to the removal of the governor last month and to some urgent repairs being carried out on one wing.
"There is a culture of denial," said Leanne Devine, a lawyer with Broudie Jackson Canter who regularly takes action against HMP Liverpool on behalf of inmates and their families.
"We've not seen any evidence of change.
"What is frustrating for the families is when they go away and they hope for change and then they see years later, coming through the press, the same cases, the same failings."
A Ministry of Justice spokesperson said: "We do not comment on leaked reports."