LEIGH SALES, PRESENTER: A mysterious billionaire property developer has worked his way into the inner circles of federal politics just four years after moving here from China.

Huang Changran is one of Australia's top political donors, pouring money into the coffers of both the Labor and Liberal parties.

It's allowed him to build ties to the country's most powerful people and raises serious questions about a loophole in the political donations system in Australia.

Despite his influence, he's remained out of the public eye - until now.

Dylan Welch and Jodie Noyce with this report.

DYLAN WELCH, REPORTER: He's one of Australia's top political donors.

ERNEST WONG, NSW LEGISLATIVE COUNCILLOR: If you want to rank him number one, probably you can.

DYLAN WELCH: But just who is the mysterious Mr Huang?

Hi. I'm Dylan Welch from the ABC. Do you have someone who can...?

For a man who arrived in Australia only four years ago, Huang Changran has made big strides. Not just anyone gets to do this:

(Huang Changran presenting trophy at 2013 Melbourne Cup Carnival)

He paid for Trade Minister Andrew Robb to go to the races that day. And Robb is just one among his many political friends.

It's no surprise he's got friends in high places. Since 2012, Huang and his company have donated just over $1.9 million to the Labor and Liberal parties.

NATHAN REES, NSW PREMIER, 2008-'09: It's poisonous and that's, that's - that's not just my view. That's the view of many people on the street. They simply can't understand why a property developer, or anyone else for that matter, would make large-scale donations to a political party.

ERNEST WONG: So I think that is that they just find making friends to them, particularly making friends to politicians, to them is a very normal, legitimate thing.

DYLAN WELCH: In about a decade, Huang amassed a $1 billion fortune in his home province of Guangdong. He came to Australia in 2011 and bought a $12.8 million home in one of Sydney's richest suburbs.

Huang's company Yuhu has made 18 donations to Labor and the Liberals, dropping as much as $200,000 at a time. Huang's wife, Jiefang, has also donated $100,000. A person sharing Huang's last name and his home address also donated $200,000.

The donations were mainly given in the weeks around the 2013 federal election. Before the election, Yuhu gave most of its money to Labor. After Abbott won, the money went overwhelmingly to the Liberals.

JOO-CHENG THAM, UNI. OF MELBOURNE: I think the AEC records indicate that Yuhu is a very significant donor to the major parties. In the 2013-2014 financial year, for example, Yuhu made $685,000 in donations to the Liberal and the Labor Party, various branches of the major parties.

DYLAN WELCH: Under federal election law, it's an offence to make donations on some else's behalf unless that's declared on your donor return. Huang's generosity appears to have inspired his staff, with two young employees making sizeable donations.

Anna Wu is a 25-year-old marketing manager with one of Huang's companies. Her LinkedIn profile says until late 2012 she was a barista at a Sydney chocolate bar.

Last year, the day before the crucial West Australian Senate election, Wu donated $50,000 to the Liberals' WA branch.

Zhaokai Su is a 29-year-old Yuhu office manager. In 2013 and 2014 he donated $130,000 to the New South Wales ALP.

7.30 asked Zhaokai Su and Anna Wu to confirm the donations were on their behalf. Both declined to comment.

So I just wanted to ask Mr Huang why it is he makes so many political donations in Australia.

HUANG ASSOCIATE: He has some next appointment, so we're going to make an appointment with you.

DYLAN WELCH: OK. I'll give you my card.

NATHAN REES (Nov. 14, 2009): From today, the NSW Labor Party will ban donations from developers.

DYLAN WELCH: Since 2009, property developers have been banned from donating to NSW politics, but they've found the ban easy to get around. Due to a blind spot in federal law, developers can still donate to federal campaigns run by the state branches.

JOO-CHENG THAM: I consider this a massive loophole because it allows for the entities to be regulated by NSW election funding laws, right? The NSW political parties to actually receive thousands of dollars, in this case hundreds of thousands of dollars, for campaign purposes.

DYLAN WELCH: Huang has developed particularly close relationships with two former heads of the ALP in NSW.

As NSW General Secretary, Sam Dastyari nurtured the ALP's relationship with Huang. At last year's launch of the Australia Guangdong Chamber of Commerce, Dastyari was effusive.

SAM DASTYARI, FEDERAL LABOR SENATOR (2014): The demonstration, Mr Huang, of how highly you're respected, how much all of us respect you and the work you do.

DYLAN WELCH: Three weeks later, he declared Huang's company had paid a legal bill that Dastyari incurred as part of his role as NSW General Secretary. The bill was in the area of $40,000.

ERIC ROOZENDAAL, FORMER NSW LABOR POLITICIAN (May 9, 2013): It would be fair to say that my time in this parliament has been a bit of a rollercoaster ride.

DYLAN WELCH: When former NSW Treasurer Eric Roozendaal left Parliament in 2013, hounded by corruption allegations, he was a man in need of a job. He found one with Mr Huang and Yuhu.

NATHAN REES: I don't think it would surprise anyone that he went there, put it that way. Mr Roozendaal, in my view, had a very significant impact on the culture of the NSW Labor Party when he was General Secretary. He was a very effective fundraiser.

DYLAN WELCH: OK. But can I ask why it is that he makes so many donations?

HUANG ASSOCIATE: He wasting a lot of time. He'll go to next appointment, so probably will do interview next time.

DYLAN WELCH: Alright. Well I hope to speak to you again soon.

HUANG ASSOCIATE: OK. Thank you very much.

FENG CHENGYI, UTS CHINA STUDIES: Political donation in China is one way to establish your status, you know, for the smooth operation of your business. He just simply might think that will deliver here as well.

DYLAN WELCH: Little is known about Huang's background in China. By the late 2000s, he was a major property developer in Guangdong. He had a close relationship with the mayor of the city of Jieyang, Chen Hongping. So close, that in 2010, Huang donated a $32 million traditional pagoda to the city. A year later, Chen Hongping was charged with receiving tens of millions of dollars in bribes from local property developers. Huang was not implicated in the case, but migrated to Australia late the same year.

7.30 approached Sam Dastyari, Eric Roozendaal, almost a dozen federal politicians and several Labor and Liberal Party executives for this story. Not one was willing to go on camera and discuss the billionaire property developer.

NSW Upper House member Ernest Wong is a friend of Huang's.

ERNEST WONG: He is actually one of the top 100 philanthropist in China, as a matter of fact. And then he - I shouldn't say that - he thinks himself a "scholar", which I think he is, because he's very knowledgeable.

DYLAN WELCH: In the end, Huang also declined an interview with 7.30 and his lawyer only provided a short statement saying the billionaire is an Australian resident and businessman and holds no public office. It seems the man who's become one of Australia's biggest political donors is content to remain a mystery a little while longer.

LEIGH SALES: Dylan Welch and Jodie Noyce with that report.