The global sports betting market is worth more than $US1.0 trillion, the vast majority of which is generated by illegal gambling, a United Nations conference has heard.

Addressing the summit in Doha on Wednesday, Patrick Jay, a British-based independent betting expert, said about 65 per cent of that global figure was spent on football betting, with the Asian market the centre of sports gambling.

Tennis and cricket account for a further 12% each, said Jay, who was speaking at a session on match-fixing in sport at the week-long UN Congress on Crime Prevention and Criminal Justice.

Jay said a conservative estimate was that the betting market was worth about $US1 trillion.

However, he said afterwards, he thought the figure was much higher.

"The trillion is all global sports betting, of which the illegal amount would be 90% of it," he told AFP.

"I'll let you into a secret," he continued. "I say the trillion figure because I can just about get away with it without being laughed off stage. The fact of the matter is, the vast majority of people think it is less than that, the only three or four people in the world that I actually respect on this thinks it is two or three times that. And it is growing."

Jay, a former director of trading at the Hong Kong Jockey Club, said illegal gambling in Asia was driven by matches that are shown live on television and played at the right time for a betting audience.

He added that "China is becoming the epicentre of the problem" and that up to one billion euros can be gambled on a single game of football.

UNODC and the Doha-based International Centre for Sports Security (ICSS), which tries to promote integrity in sport, hosted the meeting.

The two organisations announced a new partnership on Wednesday to "strengthen investigations and prosecutions into match-fixing", which includes proposed measures such as increased data-sharing, protection of whistle-blowers and seizure of assets for those implicated in wrongdoing.