Up to 4,000 prisoners in England and Wales are to be released to control the spread of the coronavirus, the Justice Department said.
Prisoners who have two months or less to serve will be released on bail in stages.
Selected low risk offenders will be tagged electronically and may be recalled at the first sign of concern.
It is seen as a way to prevent thousands of prisoners – many of whom share cells – from being infected.
In 29 prisons, 88 prisoners have tested positive for the virus and another 1,200 are said to be self-insulating.
Sex offenders and those convicted of violent or sexual offenses, as well as anyone who poses a national security problem or endanger children, will not be counted for release, said the prison service.
No detainee convicted of Covid-19 offenses – including rescuers’ coughs or theft of personal protective equipment – will also be eligible, the Department of Justice (MoJ) said.
Lord Chancellor and Secretary of Justice Robert Buckland QC said: “This government is committed to ensuring that justice is done for those who break the law.
“But this is an unprecedented situation because if the coronavirus becomes established in our prisons, the NHS could be overwhelmed and more lives at risk. “
The Justice Ministry also said that no prisoner with symptoms of coronavirus would be released, nor would those without housing and health care in place.
Buckland previously announced that pregnant inmates may be granted temporary release to protect them and their unborn children from the coronavirus.
Mothers behind bars with their children who pass the same checks could also be released, he said.
Measures legislation is expected to be in place on Monday.
It’s the last thing Boris Johnson’s government ever wanted to do.
In their general election manifesto, the Conservatives promised that criminals would be “kept away from our streets”. Since then, a series of measures have been announced to ensure that those convicted of the most serious crimes – including terrorism – remain behind bars longer.
An emergency early release program, which means that almost 5% of the prison population in England and Wales will be released before they reach half their sentence, was not a decision easy to take for number 10.
More politically acceptable options have been considered, such as the transfer of prisoners to military bases and immigrant removal centers, but they face practical difficulties.
The danger to the government of this system – the greatest since 80,000 offenders were released early in the end of work detention program between 2007 and 2010 – is that some of those released will commit new crimes, perhaps horrible.
Ultimately, the ministers decided that the alternative – infected prisoners overwhelming hospitals – was even worse.
The prison union welcomed the news, but expressed concern over the pressure from staff.
About 8,000 prison staff are absent due to Covid-19 problems, about a quarter of the total staff.
Ian Lawrence, general secretary of the Napo union, said members of the National Probation Service and community rehabilitation companies were “already overwhelmed.”
“Probation providers must ensure that this new cohort can be safely supervised and not create additional operational pressure and stress for the workforce,” he added.
In Northern Ireland, up to 200 offenders are released early and the Scottish government is considering similar measures.
France has also announced plans to release 5,000 prisoners as soon as possible, as well as 3,500 in the US state of California.
Australia, Germany and Canada have already given the green light for the early release of prisoners.