Strangeways nick has been put on a week-long lockdown with inmates confined to their cells and unable to exercise or even shower.
HM Prison Manchester has forbidden convicts from leaving their rooms for any reason amid a high security "intelligence-led" operation.
Visits at the category A jail, also known as Stangeways, have been suspended since Monday.
Relatives told Manchester Evening News how the inmates have no fresh air and are having meals brought to their doors.
The Ministry of Justice (MoJ) said the lockdown is due to an "intelligence-led operation" which has taken place inside the prison to crack down on illegal goods.
Officials confirmed that visits have been temporarily suspended and are expected to resume this weekend.
But bosses did not confirmed when the lockdown will end.
One woman, whose 19-year-old son is an inmate at the jail, told how the mood inside had become "very tense."
She said: "My son rang me to say the prisoner's mental health is deteriorating quite quickly.
"They say they haven't had showers and are being delivered one meal a day to their cell.
"He said they haven't had fresh air since last Wednesday.
"I know they are all in there for crimes but they do have human rights and this really isn't good for their mental health."
The mum added: "It's been bad enough but because of the bank holiday it will be about eight or nine days now without any visitors.
"He says prison officers have been going in to search people's cells."
Another woman, whose partner is also an inmate, said she was told how prisoners have been locked down for four days unable to shower or exercise.
She described hearing prisoners kicking their doors and alarms ringing in the background when she called the jail.
Another man, whose friend is at the jail, said: "They got a letter last week to say the prison was going into lockdown and it was expected to last a week might take longer.
"He has been behind his door for five days.
"The person I know said today will be his sixth day without a shower.
"Prison guards are bringing meals round to their cell and they are not even letting them out for dinner. He said his head is starting to go.
"Surely they have basic human rights and should be able to have a shower.
"They haven't even been let out to exercise. They have an in-cell phone system so he's been able to ring me but he can't leave his cell."
The MoJ commented on the one-week lockdown.
A spokesperson said: "An intelligence-led operation has taken place this week to crack down on the illegal contraband that puts prisoners and staff at risk.
"Visits were suspended temporarily but are expected to resume this weekend, while phone calls to family and friends have been available throughout."
