The Home Office is drawing up plans to release thousands of prisoners early, to free up cells in overcrowded jails.
Prisons in England and Wales are very nearly full
Inmates in England and Wales could be released 10 days early under the plans.
The prison system is nearly full and has room for only another 700 inmates - hence plans to extend what is called the "transitional home leave" scheme.
The scheme would not apply to sex offenders or violent criminals, but to "low-risk" inmates serving between four weeks and four years.
Nor would it apply to foreign nationals who were due for deportation.
However, the Police Federation, which represents rank and file officers, criticised the plan and said "there was nothing more demoralising" for police and victims of crime to see offenders released early.
Meanwhile, the Home Office said ministers were "seriously considering" the plan, but no decision had yet been taken, said the BBC's home affairs correspondent Danny Shaw.
However, our correspondent said that with few other short-term options available, the plan was likely to get ministerial approval.
The latest official prison population figure was 79,010, which means prisons are at bursting point.
A Home Office spokeswoman said: "The new home secretary has made additional prison places a high priority.
"In July, he announced that a further 8,000 prison places will be built to manage the pressures on the prison population following the recent review of the criminal justice system.
"In the meantime, a number of options for managing the prison population are being considered, but no decision has been taken."
But Police Federation vice chairman Alan Gordon said "all too often" offenders' failure to complete supervised rehabilitation programmes resulted in them returning to a "life of crime".
"So a short-term fix by the government just results in a long-term problem for society," he said.
Mr Gordon added: "Prisoners should serve their full sentences and if we need more prisons then let's build them.
"Whilst the idea being considered by the Home Office may just be to release 10 days early, that is 10 days less rehabilitation and 10 days more to re-offend."
However, the Prison Reform Trust (PRT) welcomed the plan to reduce the prison population, but warned much more preventative work was needed.
PRT director Juliet Lyon said: "It's good to see government at last considering how to reduce prison numbers to sensible, safe levels, but bad that this comes as a knee-jerk reaction to a crisis of its own making, driven not by crime rates but by tough political posturing and ever harsher sentencing."
She called for more investment in preventative work such as with young people at risk, court diversion for mentally-ill people and treatment for addicts.
Last week it was reported that young offenders who could be released early from institutions were to be identified as quickly as possible to stop youth prisons overflowing.
This week, London's Pentonville Prison announced it was cutting its inmate numbers by 116 to 1,011 after 14 of its prison officers were suspended due to corruption allegations.
Brian Caton, general secretary of the Prison Officers Association (POA), warned other prisons could be affected by a "shuffle the pack" policy.