Watchdog estimates that fraud is costing every adult in UK £1,500 a year

But the National Fraud Authority (NFA) admitted its figure – almost twice the amount shown in last year’s report – was only a “best estimate”. It claimed the private sector suffered losses of £45.5bn, but this was based on “opinions not facts” from a self-selecting survey of just 37 businesses.

Stephen Harrison, the NFA’s chief executive, insisted the figures were the “best collective estimate of the impact of fraud on our country”.

“We did our best with the information that was available to us,” he said. “Fraud is an under-reported crime.

“And in some cases it can be a challenging crime to measure.”

In a briefing in which officials were repeatedly questioned over the reliability and use of the headline figures, Mr Harrison said the annual fraud indicator “leads to better strategies, raising awareness, preventing fraud and bringing more fraudsters to justice”.

“By tackling the potential scale of the problem, we can help motivate sectors to tackle fraud in an effective way,” he said.

The watchdog said fraud cost the UK £73bn a year, almost double last year’s estimate of £38.4bn, but insisted this did not reflect an increase in fraud, saying it was simply the result of better estimates.