However, the NAO believes a "central understanding of the risks to services is vital in a time of major restructuring, with systems to identify when the potential risks materialise and the ability to respond rapidly".
Amyas Morse, head of the NAO, said that the £5.5 billion savings, achieved at a running cost of £72 million, highlight value for taxpayer's money - but the organisation needs to address how it will continue its success in the future.
"Nearly three years on from its birth, the Efficiency and Reform Group is clearly helping departments achieve substantial reductions in annual spending. This demonstrates that the ERG is providing value for money," said Morse.
"As a relatively new organization, ERG has assessed the obstacles it faces and has begun to tackle them energetically. However, it needs to get going on moving beyond the role of imposing central spending controls to placing more emphasis on changes aimed at promoting sustainable savings."
The report, interestingly, also highlighted that ERG faces staff shortages and a lack of key skills in some areas - particularly in commercial experience at a senior level, and staff with systems experience.
"Some parts of ERG, for example, ICT and commercial models, have reported difficulties in recruiting staff with the right experience," reads the report.
The NAO recommends that going forward ERG should develop and publish a clear vision for how it will help departments make longer-term savings, report publicly on the likelihood of meeting its savings forecasts in each area of its activity and work with departments to undertake an assessment of the risks they face in delivery the efficiency and reform programmes.
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