Expansion of electronic tagging in England and Wales will put public at risk, watchdog warns

National Audit Office says system needs to be upgraded before it is extended to ease strain on overcrowded prisons

The rapid expansion of electronic tagging to reduce pressure on prisons will put public safety at risk without robust improvements to a system already under significant strain, the UK’s public spending watchdog has warned.

The number of people in England and Wales being electronically monitored has doubled to 28,700 over five years, and is estimated to rise to 22,000 tagged each year from 2027 under government plans to combat the prison capacity crisis by managing more offenders in the community.

But thousands of individuals may not be actively monitored, the National Audit Office said in a report that raises serious questions about the effectiveness of the system. It calls on the Ministry of Justice (MoJ) and the HM Prison and Probation Service (HMPPS) to put robust contingency plans in place.

As of March 2026, HMPPS was reviewing about 8,900 cases – 24% of those required to be tagged – to determine the number of unmonitored cases, the report said. The MoJ suggested the figure was lower, saying its statistics show unmonitored cases to be around 5,450.

Among its concerns, the report highlighted poor early performance from one external contractor, Serco . Between August 2024 and July 2025, individuals were not tagged on time and officials were not notified of potential breaches in a timely manner, though performance was said to have since improved.

During this period, the backlog of visits to fit, check or remove tags increased significantly to a peak of 7,000 in October 2024, before returning to fewer than 400 in November 2024, the report said.

There were delays in fitting individuals with tags. In February 2026, although Serco met its 95% timeliness target for visits, it was only successful in fitting tags on 62% of the people it visited within its two attempts.

An estimated shortfall of about 2,200 probation staff as of March 2026 also added to concerns about whether the system could scale up safely, the report said. It concluded that further expansion to the electronic monitoring system would not be efficient or effective unless the MoJ and HMPPS worked with partners to address weaknesses in governance, data quality and system-wide inefficiencies to support a more reliable and responsive service.

The government has allocated up to £175m to fund the expansion over the years of 2026-29.

G areth Davies, the head of the NAO, said: “ Electronic monitoring is central to managing pressures on prisons, but it is not working effectively, creating risks to public protection. The MoJ and HMPPS should address the inefficiencies and risks identified in our report before expanding electronic monitoring.”

Sir Geoffrey Clifton-Brown, the chair of the public accounts committee, said the report raised serious questions. “Most concerningly of all, the government does not know for certain how many people who should be tagged are being left unmonitored, nor does it have the information or capacity to respond quickly to breaches, resulting in unknown risks to public safety,” he said.

“ The government needs to improve the service’s resilience and efficiency, otherwise expanding electronic monitoring risks wasting public money and puts public safety at risk.”

Pia Sinha, the chief executive of the Prison Reform Trust, said the findings were a “cause for concern”.

“As ministers look for ways to manage prison overcrowding, there is a risk of seeing electronic monitoring as a panacea,” she said. “Expanding the use of tagging without addressing wider pressures risks undermining both public confidence and public safety.

“The government should take the NAO’s findings seriously and ensure that any further expansion is accompanied by investment in probation, robust safeguards and a clear understanding of what success looks like. Electronic monitoring can be an effective tool, but only when they are part of a well-functioning system that enables people to rebuild their lives and reduce reoffending.”

An MoJ spokesperson said that the government had inherited “a failing tagging system with record backlogs” and noted that install rates had risen by almost 50% since 2024.

They added: “Public protection is our priority, which is why we’re investing £100 million in electronic monitoring, tagging offenders before release for the first time and strengthening victim protections via new alert systems – all of which will help cut the number of unmonitored offenders.”

They also pointed to a £700m investment in the probation system, and the hiring of additional trainee officers.