More than £3.6m of losses to the public purse are estimated to have been stopped by Oxford-based fraud investigators in their first year of operation.
Oxford City Council's investigations team has already saved the taxpayer £3.3m in 2015/16 and this figure is expected to rise by another £300,000 by the end of the financial year, a report shows.
It was launched last April after the government changed the way councils investigate fraud and within its first month had already paid its own running costs.
Types of fraud it tackles include people who are wrongly trying to access council tax discounts, the right-to-buy and social housing.
And the team has now expanded its activities to cover Oxfordshire – in partnership with the county council – to target people wrongly using blue badges.
Investigations team leader Scott Warner said: "The level of success so far has been a surprise and we are extremely pleased to be where we are. With the development of technology and new methods, we are detecting and preventing more and more fraud. The chances of offenders getting away with it are drastically reducing."
Mr Warner revealed officers have beefed up their capabilities by bringing in new computer systems that can compare vast amounts of national data with local records.
It will enable them to carry out more checks for fraud like the data-matching exercise in 2013 that led to the conviction of Oxford couple Kevan Barrett and partner Kerri Kinsey last year, who wrongly claimed £203,395 in benefits.
Since the changes made by the government last year, councils no longer investigate housing benefit fraud, but Mr Warner's team now focuses on stopping the council being defrauded.
This means stopping people from wrongly claiming council tax discounts and the right-to-buy, confiscating ill-gotten cash and taking back houses from people who have supplied misleading information.
Mr Warner added that the council is now looking to work more with neighbouring authorities.
He said: "Using data from partners we can tackle cross-boundary fraud, look at trends and take action before problems develop. It is all about staying one step ahead."
City council deputy leader and finance chief Ed Turner said: "I am really proud of the work our investigations team has done. Clearly – although they are a minority – there will always be people who try to rip off the council or access things they are not entitled to by giving information they know to be wrong. They can take up council homes that are desperately needed by families and, given the scarcity of housing, that is a real concern. Fortunately, the chances of them being caught are that much higher in Oxford because of the good work being done here."
So how much more fraud is there to uncover?