Statistics question

You know that figure of 'only 0.7% of the welfare budget is lost to fraud' figure that gets thrown around in comparison to tax avoidance/ evasion?

Does anyone have a citation with the data that's based on, please? I ask because a 0.7% incidence is lower than any statistically significant margin of error I've ever seen and I'd like to look at the original numbers to see how they came by it.