A team of prison inspectors pulled out half way through a week-long inspection of Holloway prison, in north London, shocked by appalling living conditions and a harsh security regime.
The unprecedented move is being seen by prison reform campaigners as a determined early show of strength by the new HM Chief Inspector of Prisons, Sir David Ramsbotham, who took over the job earlier this month.
The team of 11 inspectors began their unannounced check of Britain's biggest women's prison on Monday last week.
However, they pulled out early, on Thursday, appalled by what prison sources describe as "the incredibly tense atmosphere" and "very bad living conditions" inside the jail.
A statement from the inspection team said: "Our early findings identified such shortfalls in the treatment of prisoners and in the conditions at Holloway Prison that the proper course for us was to seek immediate improvements."
After the withdrawal, Sir David wrote to the head of the Prison Service and the Home Secretary saying the team would not return until conditions at Holloway had improved.
It is understood the inspectors were concerned about an apparently over- zealous and heavy-handed security regime.
One prison employee told the Independent that the increase in lock-up times from 12 hours a day to between 21 and 23 hours a day was a key cause of the general malaise inside Holloway.
Security was tightened up in the wake of the two reports into the Parkhurst and Whitemoor break-outs.
Overcrowding has added to poor conditions in the jail, said the staff member. At the end of November the prison held 543 women, more than a quarter of Britain's total female prison population.
The employee also said extensive refurbishment work and an infestation of pigeons make things worse and that sickness among staff is high because of stress caused by overwork.
Staff now fear their governor, Janet King, who is generally well-regarded, will be made a scapegoat.
Prison reform campaigners saw the sudden withdrawal of the inspectors as an indication that the new HM Chief Inspector is prepared to insist on the humane treatment of inmates.
Frances Crook, director of the Howard League for Penal Reform, said the withdrawal followed more than six months of mounting worries over Holloway.
Complaints from inmates, visitors and members of staff at the prison had referred to excessive use of shackles, denial of access to education, 24-hour confinement and heavy-handed security, she said.
There were reports of pregnant inmates being shackled until they went into labour and having their chains put back on immediately after the birth, she added.
Holloway was heavily criticised by Sir David Ramsbotham's predecessor, Judge Stephen Tumim, in his 1992 report on the prison. In it he said he "deplored some of the arrangements for the Mother and Baby Unit" which was housed in a "cockroach infested semi-basement, looking on to a dirty yard".
Since his report, conditions did improve, but this recent withdrawal by inspectors signals that standards have slipped again.
Earlier this month Richard Tilt, the acting Director General of the Prison Service, warned governors about getting the balance right between security and control on the one hand and rehabilitation and justice on the other.
"I have heard some people argue that we are in danger of tipping the balance too far in favour of security. There have been references to an unjustified 'orgy' of security," he said.
The Prison Service said last night that their senior officers had been working with Holloway's governor to resolve the areas of concern.