Steve Vickers, a former head of criminal intelligence for the Royal Hong Kong Police who now runs a corporate risk consultancy, told the inquiry on Monday that China's anti-gambling laws and limits on taking cash out of the country meant it was impossible to keep Triad gangsters out of the junket industry.

"Triad activities in junkets are notorious and well known to everybody, frankly, that knows which way is up in Macau," he said.

"The capital controls exist in China, it's still illegal to promote gambling in China, it is difficult to enforce gambling debts in China - that's the underlying cause as to why Triad societies are around."

Mr Vickers said junkets would invariability need "people who are tough, who are capable of exercising persuasion, of violence to collect" gambling debts incurred at overseas casinos using the junkets' credit.

However, Mr Vickers said it was possible for regulation to limit criminal influence in the industry. The gold standard was Singapore, he said, where the gambling regulator conducts its own "ruthless" due diligence of any junket a casino wants to works with.

"As a consequence, they have successfully eliminated the bulk of the well-known Triad chaps," Mr Vickers said.