A total of 55 prisoners have now tested positive for coronavirus in the UK, the Ministry of Justice has said.
The inmates are housed across 21 prisons.
In addition, 18 prison staff and four prison escort staff have tested positive.
The total number of cases has doubled since the last update on Friday, when 27 prisoners were confirmed to have tested positive.
In its daily update, the MoJ said it had temporarily paused the usual regime in prisons so it could implement the government’s measures to encourage the public to stay at home, protect the NHS and save lives.
“This is to ensure prisons are complying with social distancing rules and to protect staff and prisoners,” it added.
It said the government had moved quickly to keep prisoners in touch with their family members during the coronavirus crisis – providing 900 secure phone handsets across 57 prisons.
The MoJ also ensured that prisons are prepared to take immediate action wherever cases or suspected cases are identified, including the isolation of individuals where necessary.
Ministers are being urged to release prisoners during the pandemic after Northern Ireland signalled it would let out more than 10% of those behind bars.
Justice Secretary Robert Buckland has been under pressure to allow convicted criminals to go home in a bid to prevent more deaths in England and Wales’ crowded prisons.
Staff numbers in prisons are already stretched, with some 3,500 employees – around a tenth of the workforce – currently in self-isolation due to COVID-19.
In Northern Ireland, justice minister Naomi Long announced the temporary early release of up to 200 prisoners.
Meanwhile, Scotland’s justice secretary Humza Yousaf said on Friday that he was “actively considering” options for the early release of prisoners.
The Independent Advisory Panel on Deaths in Custody (IAPDC) said prisons should be only for “serious and violent offenders” at this time, with judgements made on a “case-by-case basis”.
Kate Allen, Amnesty International’s UK director, said last week that decreasing the prison population and the number of people in immigration detention centres is “a crucial means of slowing the spread of COVID-19”.
She added: “We urge the government to follow the lead of governments in Northern Ireland and Scotland and provide alternatives to detention for those with underlying medical conditions, and older people, if they do not pose a threat to themselves or society.”
As of Monday, 134,946 tests have been carried out across the UK; 112,805 were negative and 22,141 positive, said the Department of Health and Social Care.
A total of 1,415 people have now died in the UK after contracting coronavirus – following 180 more deaths across the country.