There has been a 90% increase in the number of cases of major fraud in the South West over a 12-month period.
Cases of major fraud in 2003 involved just over £14m
Major fraud is classed as any case that goes to court where the sum involved is in excess of £100,000.
Some 19 cases went to court in 2003, compared with 10 in 2002, according to a "barometer" used by accountants KPMG.
However, although the number of cases increased, the total value of the money involved fell from £27.5m in 2002, to just over £14m in 2003.
One case involved a man who posed as a police offer to try to extort £120,000 from an Exmouth widow, claiming that two men were planning to kidnap her son.
Another case involved a businessman from Cornwall who, along with an associate, was alleged to have claimed more than £1.4m in false agricultural subsidies to boost a flax business.
A spokesman for KPMG's regional forensic unit warned companies in the South West were potentially at risk from fraud from both inside and outside the organisation.
Jonathan Middup said: "The barometer shows that more frauds than ever are being committed, with organisations being attacked both internally and externally.
"There are some individuals who will commit fraud if they are given the chance, and many businesses are leaving themselves open to attack by not having adequate fraud risk strategies, whistle-blowing policies or internal processes to minimise the opportunity."
"The key message for businesses across the region is: do not be complacent about fraud.
"There are organised criminals who are actively targeting companies. Internal controls must be robust to prevent management, employees, customers or suppliers from exploiting weakness in systems.
"Fraud can seriously damage not only the financial basis of a business, but also its reputation."
In a trend matching that of the South West, the total value of fraud in the UK declined to £374m in 2003, a 48% decrease from 2002's £716m.