One of Asia's biggest unregulated bookmakers — an alleged organised crime figure with links to Australia — has been identified by state and federal law enforcement as a potential threat to the integrity of sport across the country.

Key points: Bookmaker Wei Seng "Paul" Phua is an alleged organised crime figure and a valued client of Crown Casino

Bookmaker Wei Seng "Paul" Phua is an alleged organised crime figure and a valued client of Crown Casino Identified by authorities as a threat to integrity of Australian sport

Identified by authorities as a threat to integrity of Australian sport NSW police don't know full scale of offshore gambling enterprises

NSW police don't know full scale of offshore gambling enterprises Revelations come amid tennis match-fixing scandal

Wei Seng "Paul" Phua, a Malaysian high-roller behind one of the world's largest unregulated sports betting websites, has also surfaced as a highly valued client of Crown Casino in Melbourne.

A Four Corners investigation has confirmed that despite his well known criminal associations, Crown Casino even flew Mr Phua into Melbourne three weeks ago on board one of its corporate jets.

These bookmakers — whose companies are registered in jurisdictions like Manila, Curacao and the Isle of Man — have found large black markets across Asia where sports betting is wildly popular but often illegal.

It is estimated more than two-thirds of all money bet on sport worldwide is bet with these unregulated operators.

"We know that they're accepting bets roughly of about $2 billion every week," Victoria Police Assistant Commissioner Neil Paterson said.

"It's estimated globally that the unregulated betting markets that operate across all sports are worth between $1 [trillion] and $3 trillion annually."

The Four Corners investigation into these bookmakers has shed new light on their connections with organised crime and match-fixing syndicates.

The revelations come in the midst of a global match-fixing crisis in tennis, raising new questions about the ability of sport's governing bodies and police around the world to root out corruption and deter criminal infiltration.

The program has confirmed, for example, that the match-fixing syndicate that in 2013 targeted some members of the Southern Stars Victoria Premier League soccer team — to date the biggest match-fixing scandal to hit Australia — was using opaque Asian bookmakers to place its bets.

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Police struggle to understand scale of threat

NSW Police Detective Superintendent Scott Cook said offshore bookmakers posed a risk because they were utterly opaque.

"We don't really know the full scale of what goes through these businesses," he said.

"This impacts us in Australia, particularly in NSW, with regard to a lot of sports and other gambling enterprise, simply by virtue of the internet and the transnational nature of what's going on.

"We don't fully understand how big it is and I'm not even sure that we can ever determine the parameters or the size of the problem."

Assistant Commissioner Paterson said Mr Phua's background was typical of the industry in Asia.

"Paul Phua is a major player, we know that he has links into some of the unregulated betting markets that operate in the Philippines," he said.

"The FBI operation was able to bring out into the open some of the information that now is known around him, and it gives us great concern the sheer volume of money that passes hands in this area, of the organised crime links in that space as well."

The FBI alleged, in a Nevada court indictment, that Mr Phua is a "high-ranking member" of the feared Asian crime syndicate, the 14K Triad.

A federal law enforcement source told Four Corners Mr Phua "has bet tens of millions of dollars in Australia".

The top-level source said Commonwealth investigators identified connections a decade ago between Mr Phua and the Hells Angels outlaw motorcycle gang in both Canada and Australia.

Mr Phua declined to respond to questions from Four Corners, as did Crown Casino.

He made a substantial fortune sourcing high-rolling baccarat players from across Asia for Macau's casinos, setting up a VIP junket called Star 888.

Such junkets are responsible for bringing many billions of dollars into China's gambling hub, and into other casinos across the world.

Crown Casino declined to say whether Mr Phua had ever brought junket tours to its resorts in Melbourne or Perth.

FBI investigation exposed Phua's links to gambling site

Mr Phua was first revealed as the secret controller of the massive online gambling website IBC (since rebadged as Maxbet) during the FBI's investigation in 2014.

Before then, the true owners of the company had been veiled by layers of corporate secrecy.

Mr Phua's close business associate, Seng Chen "Richard" Yong, was convicted, and then later acquitted in 1998, of running an illegal gambling operation in Hong Kong. These days Mr Yong is also a valued client of Crown Casino.

When Mr Yong's hotel suite in Las Vegas was raided by US authorities they discovered a 24-carat gold-plated iPad stamped with a Crown Casino insignia.

Another significant figure, who appears in the FBI's case materials, is Cheung Chi Tai.

A copy of his passport was saved onto the laptop of one of Mr Phua and Mr Yong's associates and labelled "BOSS HKSAR PASSPORT 2011".

Mr Tai was named in 2011, in the Hong Kong High Court, as a Triad boss and mastermind in a murder conspiracy.

He was charged last year in Hong Kong with laundering $HK1.8 billion in criminal proceeds — a charge he denies.

By March 2015, Mr Phua's son Darren Phua, and five other associates, pleaded guilty in Nevada to illegally transmitting gambling information while running a book worth hundreds of millions of dollars on the soccer World Cup — including on games involving the Socceroos.

The elder Phua fought the charges. His lawyers successfully argued that the FBI's evidence — including reams of electronic surveillance — had been unconstitutionally obtained.

The FBI case came just weeks after Mr Phua had been arrested in Macau and "charged with organised crime and operation of illegal gambling".

Sorry, this video has expired Macau Police parade IBC operatives, including Wei Seng "Paul" Phua, in front of local media

Phua's visit to Melbourne coincides with major poker tournament

At the time of his arrest in Macau, Darren Phua worked the phones according to the FBI's case, trying to get assistance for his father. He contacted a prominent Greek businessman, Petros Stathis, to alert him to his father's predicament.

Mr Stathis immediately set about checking Interpol alerts for any further information about Paul Phua and, via text message, offered the assistance of several high-powered friends: "Let me know ... if I need to activate prime minister or San Marino m of Foreign Affairs."

At one point Darren Phua sent a message to Mr Stathis: "Hey brother. We just received a call from Macau saying that the one who arrested Paul is a friend of Paul and they are negotiating now. Hopefully they want money only."

Several days later, Paul Phua flew out of Macau on board his Gulfstream jet.

Three weeks ago, he left his own jet at home for his trip to Australia. Shortly after midday on January 9, one of Crown Casino's new fleet of jets, carrying the tail sign VHCCX touched down in Melbourne with Mr Phua on board. Two days later, Crown Casino flew him home.

It is not clear why Mr Phua spent only two days in Melbourne. His visit coincided with a flashy poker tournament hosted each year at Crown Casino called Aussie Millions, the kind of event he might normally headline.

While Mr Phua has never been successfully prosecuted, Four Corners has established the Malaysian remains under police investigations in multiple jurisdictions.