Britain's largest jail is run by an "unacceptable regime", the prisons watchdog has warned.

In a damning report into life at Liverpool jail, the chief inspector of prisons details a catalogue of problems including an overcrowding crisis and poor industrial relations.

Anne Owers concluded HMP Liverpool was "seriously underperforming" after discovering cockroach infestations, broken windows and filthy cells.

Conditions at the jail, which houses 1500 inmates, were so bad that the prison has been threatened with privatisation.

Her report highlights dozens of problems including prisoners only being able to shower and change clothes once a week.

"At the time of the inspection, Liverpool was not delivering an acceptable regime for the prisoners in its care," said Owers.

"Conditions on the induction wing, for newly-arrived prisoners, were among the worst we have seen and standards of hygiene and cleanliness there and in the healthcare centre were unacceptable."Efforts to improve work and education facilities for prisoners - vital to breaking the cycle of offending - had actually got worse.

Despite the fact that 95 per cent of prisoners had basic literacy and numeracy problems, only 18 per cent had access to learning facilities.

The watchdog also highlighted the continuing problems between employers and the Prison Officers' Association.

The Prison Service accepted the report's hard-hitting findings and claimed improvements were already underway as the jail had been identified as under-performing.

"It was for this reason that Liverpool was selected as one of the prisons to undergo performance testing," he said.

"This process is already under way and, with additional management support, Liverpool are planning a major improvement to their regime and its delivery.

"If the bid is to be successful it will have to address the many shortcomings this report identifies."