The inadvertent releases heap further embarrassment on the Prison Service, which has been starved of resources for many years.
British police were undertaking two more searches on Wednesday, following the news that two prisoners had been mistakenly released from prison over the past week, just days after the government brought in more stringent checks.
Police said the two were wrongly freed from Wandsworth Prison in southwest London and which last year was put into special measures after another prisoner escaped by clinging to the underside of a food delivery truck.
London's Metropolitan Police said Brahim Kaddour-Cherif, 24, was wrongly freed on 29 October while Surrey Police said it is hunting for William Smith, 35, who was also accidentally released on Monday.
The Met said that it was only informed of Kaddour-Cherif's release on Tuesday, six days after the mistaken release of a man who had entered the UK legally in 2019 but had overstayed and was in the initial stages of the deportation process.
It said Kaddour-Cherif, an Algerian national who was serving a sentence for trespass with intent to steal, is also known to use other variations of his name, including Ibrahim.
It also confirmed that he is a registered sex offender, having been convicted a year ago for indecent exposure.
"Cherif has had a six-day head start but we are working urgently to close the gap and establish his whereabouts," said Commander Paul Trevers, who is overseeing the investigation.
Meanwhile, Surrey Police said Smith was sentenced on Monday to 45 months for multiple fraud offences and was accidentally freed the same day.
The inadvertent releases heap further embarrassment on the Prison Service, which has been starved of resources for many years and the new Labour government, which returned to power last July after 14 years, replacing the previous Conservative administration.
The releases come barely two weeks after the asylum-seeker at the heart of a rise of anti-immigration protests during the summer had been mistakenly let out of Chelmsford Prison on 24 October, east of London.
Ethiopian national Hadish Gerberslasie Kebatu, who had been sentenced to 12 months in prison for sexually assaulting a 14-year-old girl, was captured after a two-day search and has now been deported to Ethiopia.
After the Kebatu search, the government announced stronger security checks in prisons and launched an independent investigation into the blunder.
Deputy Prime Minister David Lammy, who is also the justice minister, said he was "absolutely outraged" and sought to blame the woes facing the prison estate on the previous government.
Shortly before news of the latest incident broke, Lammy repeatedly refused to confirm during questioning in the House of Commons whether any more asylum-seekers had been wrongly released since Kebatu had been accidentally let out of prison.
According to government figures, 262 prisoners were released in error in the year ending in March 2025, a 128% increase on the previous 12-month period.
Conservative spokespeople said the Labour government has to take the blame as the sharp increase in the numbers is directly linked with its decision to release some prisoners earlier to ensure prisons don't hit their capacity.