A failed government plan to transform the system for electronically tagging offenders wasted £98m of taxpayers’ money, Whitehall’s spending watchdog has found. The National Audit Office (NAO) said attempts to upgrade HM Prison & Probation Service’s (HMPPS) tagging system were abandoned in March after 11 years and a net spend of £153m. Ministers still do not know if electronically tagging criminals is helping to cut reoffending because of failings in the system, the NAO report says. It says Capita, the outsourcing firm that was contracted to develop the new system, called Gemini, has contributed to severe delays and spiralling costs. Dominic Raab, the justice secretary, announced a vast extension of the tagging system at the Conservative party conference, saying more than 25,000 criminals would be fitted with ankle tags as part of a £183m plan. Meg Hillier, the chair of the public accounts committee, said the HMPPS had once again allowed its ambition to outstrip its ability to deliver. “After years of poor performance, missed deadlines and almost £100m of taxpayer money down the pan, electronic tagging has failed to become the modern and effective service intended,” she said. “Despite repeated warnings by my committee on the importance of good data and evaluation, the debacle means that robust information is simply not available. [The Ministry of Justice] is marching ahead with more electronic tagging but is flying blind on whether it’s actually effective.” There were more than 15,000 tagged offenders last year, including people on bail, those who have received community orders, those on licence after their release from prison, and foreign national offenders. Tags can be used to monitor whether the wearer is at home during set periods, to track movements or to monitor alcohol concentrations in sweat. In 2011 the MoJ set out to overhaul the tagging system to make it more efficient, but the report says this has been “unsuccessful because HMPPS has failed to deliver a new case management system”. It says: “HMPPS has had to rely on old and outdated technology and fundamental inefficiencies in tagging services remain unresolved. The current system requires staff to re-enter information manually, which is slower and more prone to error.” The Gemini case management system was “intended to improve data, streamline processes and save money”, but a decision was taken in August 2021 to terminate the contract with Capita. Without Gemini, information on journeys taken by offenders is limited, and “the poor quality data means that HMPPS still does not have evidence as to whether electronic monitoring is effective in reducing reoffending”, the report says. According to the report, HMPPS and Capita “contributed to severe delays” for the transformation programme. “By the time the contract for Gemini was terminated, the programme was already 18 months late against its original, over-optimistic timetable.” Plans for HMPPS and the Home Office to monitor foreign criminals using smartwatches that capture biometric data have been delayed because the operating system “did not meet government cybersecurity standards”, the report says.