More than £2bn went missing in 2009 from businesses and the public sector, a survey by accountancy firm BDO shows.

Reported fraud smashed the £2bn barrier for the first time last year and could top £5bn within a couple of years with managers uncovering more theft as they clamp down on costs and cashflow in the recession.

The startling amount lost by businesses and the public sector to larger frauds last year is up 76% on 2008 levels.

The figures have been collected by BDO, the accountancy firm, which has one of the largest fraud investigation teams. Simon Bevan, the group's head of fraud, said: "2009 saw the steepest increase since our report began seven years ago, with the average value of each fraud now over £5m compared to £1.8m in 2003."

He warned it was a precursor of things to come: "Based on my experience of the two previous recessions, I expect that reported fraud will treble over the next two years. There has always been a lag effect, with reported fraud continuing to rise for at least a couple of years after businesses start to come out of the recession.

"A large part of this will be a tidal wave of fraudulent borrowing that has only just started to appear, particularly through use of overvalued properties as security for loans while the property market was booming. Currently many of these frauds are yet to be recognised by the banks, which still have them classified as non-performing loans."

He accused businesses of being "cavalier with regard to risk in boom times".

BDO said the cost of management fraud was up 48% and the best sales staff often turned out to be the "best fraudsters". In the financial sector, fraud was up 70% to £1.34bn, but BDO estimates 90% of larger frauds in the sector are not reported.

According to the survey, most fraudsters are aged 20-39 and the vast majority – nearly £1.8bn – are in London and the south-east. Few perpetrators have mitigating circumstances: 81% of frauds are carried out to fund a more lavish lifestyle. About 9% are linked to alcohol, gambling or drugs problems and 5% to debt. Only 1% of frauds are explained by "need" for extra cash and 2% are prompted by health issues or depression.

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