More than £83bn is laundered through gambling on sport around the world each year, according to a major new study.
The International Centre for Sports Security (ICSS) and Paris Sorbonne University estimate that 80% of sport betting is via illegal transactions, which are largely undetectable.
They say between £160bn and £400bn, about 2% of global gross domestic product, is wagered on sport each year.
"Global sports betting is at increased risk of infiltration," they said.
Chris Eaton, the director of sport integrity at ICSS, said the transformation of the nature of betting "has made suspect activity even harder to detect".
The report details how cricket and football are most at risk, but warns that tennis, basketball, badminton and motor racing are also thought to be under severe threat from criminal activity.
It suggests a number of practical solutions it believes will help combat match-fixing and illegal betting.
- creating a sports betting tax to finance investigations into match-fixing and illegal betting
- prohibiting players, coaches and administrators from betting on competitions and matches within their sport.