Thousands of offenders across England and Wales who are required to wear electronic tags are not being monitored, an audit has warned.
A report from the National Audit Office (NAO) has warned that as of March this year, prison authorities were reviewing 8,900 cases of individuals who were recorded as having an active monitoring order but no tag.
The Ministry of Justice (MoJ) has disputed this figure, reporting approximately 5,450 as the total number of unmonitored individuals. It is understood the figure proposed by the NAO refers to the number of offenders under review to check they are unmonitored.
The NAO warned HM Prison and Probation Service (HMPPS) “does not have an accurate understanding of the number of individuals that should be monitored and are not (‘unmonitored’), but this number could be significant”.
The MoJ has been urged to fix current issues with the system ahead of a significant rise in demand from September when the government is planning to enact its latest early release plan in order to ease overcrowding. Some offenders could be released from prison after serving 33 per cent of their sentence, rather than the current 40 or 50 per cent, many of whom would require electronic monitors.
Electronic monitoring, or tagging, is used in England and Wales to monitor curfews and conditions of a court or prison order. Those deemed at risk, including rapists and murderers, are fitted with ankle tags so their movements can be monitored.
Since January 2021, HMPPS has rapidly expanded electronic monitoring. The number has jumped from 13,400 to 28,700 in March this year.
The NAO reported that thousands of people were not tagged properly due to early supplier performance issues between August 2024 and July 2025, which meant officials were not notified of potential breaches in a timely manner. While the performance has since improved, the NAO warned improvements alone are not sufficient to ensure the wider system is working as intended.
Experts have warned that the NAO’s report raises questions about whether the rapid expansion of electronic monitoring was being properly resourced – especially as probation services remain understaffed.
Pia Sinha, chief executive of the Prison Reform Trust, said: "Electronic monitoring can play an important role in supporting people safely in the community, but only if it is properly resourced and there is also a focus on rehabilitation as well as compliance. The findings that thousands of people may not be actively monitored, that breaches are not always responded to effectively, and that probation services remain significantly understaffed should be a cause for concern.
“As ministers look for ways to manage prison overcrowding, there is a risk of seeing electronic monitoring as a panacea. Technology can support better outcomes, but it cannot substitute for the skilled probation staff, effective community services and tailored support that help people move away from crime. 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: “This government inherited a failing tagging system with record backlogs. As this report shows, we have worked hard to fix this, with install rates up by nearly 50 per cent since 2024.
"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.
"This is in addition to our record £700m investment in probation, recruiting 2,300 trainee probation officers over the last two years, and recruiting a further 1,300 this year - making sure the probation service has the resource it needs to keep dangerous offenders under closer surveillance than ever before."
