PRISON numbers cannot be cut with "dangerous quick fix" solutions, Justice Secretary Liz Truss will say.
The Cabinet member will use a keynote address on Monday to attack a "reckless" opposition call to reduce the current number of 85,000 prisoners in England and Wales to the 1990 level of 45,000.
Ms Truss' speech will come ahead the broadcast of a Panorama investigation which highlights in HMP Northumberland the scale of the issues facing prisons.
Loading article content
The BBC's undercover reporter said inmates were effectively running the prison, where he witnessed widespread drug abuse.
Ms Truss will say: "Reductions by cap or quota, or by sweeping sentencing cuts are not a magic bullet, they are a dangerous attempt at a quick fix."
She says Britain needs to deal with the reality of the present, rather than hark back to prison numbers of the past.
"There are those in Labour who want to turn back the clock and cut the prison population to the size it was in 1990, at around 45,000," Ms Truss adds.
"This would be reckless and endanger the public."
Ms Truss says targeting sexual offenders more effectively has pushed the prison population up.
"The biggest driver for prison growth in the last 20 years has been the exposure, pursuit and punishment of sexual offences, domestic abuse and other crimes of violence," she will say.
Ms Truss says the Government is dealing with human "wickedness" as she attacks Labour for its stance.
"Shadow attorney general Shami Chakrabarti wants to halve our prison numbers because she does not believe 'the sum of human wickedness' could have doubled in her lifetime," she says.
"She blames a political arms race for the numbers in our jails.
"What has actually happened in Baroness Chakrabarti's lifetime is that the criminal justice system has got better at catching and convicting criminals who have perpetrated some of the most appalling crimes imaginable.
"And sentence lengths now better reflect the severity of crimes like domestic violence, rape and child abuse.
"It's not that the sum of human wickedness has doubled - it's that we have driven that wickedness out from the shadows and put it where it belongs, behind bars."
The BBC's Joe Fenton spent two months undercover as a custody officer in the prison near Morpeth, which houses 1,348 men and is run by private firm Sodexo Justice Services.
Ahead of the episode on BBC One at 8.30pm on Monday, he said: "It didn't take too long to realise that the inmates were, in effect, running this prison.
"I saw prisoners stumbling around drunk, others who were high on drugs and some struggling to cope with addiction.
"Prison officers repeatedly told me they had lost control of the prison.
"I saw officers worried about their safety and losing confidence."