A Chinese government-backed propaganda unit and a swag of companies that stand to gain from the China Australia Free Trade Agreement have made more than half a million dollars of political donations in Victoria, raising concerns about the influence of foreign donors.

Companies linked to Chinese conglomerate Yuhu Group made a donation to then trade minister Andrew Robb's fundraising entity the day the trade deal was clinched.

Chinese money has become so important to Australian political parties that, at a recent glitzy fundraiser, Victorian Liberal president Michael Kroger made sure there was an interpreter to translate the auction.

Donors with strong links to China contributed $555,000 to the two major parties and fundraising entities in Victoria, a Fairfax Media analysis of Australian Electoral Commission data for 2014-15 reveals.

At least three donors failed to disclose their contributions to the Australian Electoral Commission.

Bayside Forum, which supports the federal Liberal candidate in the seat of Goldstein (where Mr Robb is set to be succeeded by former Human Rights Commissioner Tim Wilson at the July 2 federal election), accepted $100,000 in donations from executives of Chinese agriculture, property development and infrastructure company Yuhu Group.

At the time, Mr Robb was negotiating both ChAFTA and the 12-country Trans-Pacific Partnership.

Mr Robb has a long relationship with Yuhu and its chief Xiangmo Huang. He met with Mr Huang and other senior company executives in Hong Kong in March 2014 to discuss trade and economic co-operation, and to hear Mr Huang's view on the obstacles to Chinese enterprises in Australia, such as working visas and foreign investment restrictions.

Mr Robb also endorsed Yuhu's $2 billion investment in Australian agriculture in a joint-venture with a Chinese state-owned enterprise at its launch on September 15, 2014.

According to AEC disclosures, Chaoshan No 1 Trust (of which Mr Huang is a director) made a $50,000 donation to Bayside Forum two months later, on the same day ChAFTA was finalised and details announced by Mr Robb and then prime minister Tony Abbott.

Another $50,000 donation to Bayside Forum, this time by Fu Ocean Pty Ltd (whose director Zhaokai Su is reportedly Yuhu's office manager), was undated. And two months after the Hong Kong meeting, $30,000 was donated to the New South Wales division of the Liberal Party. It is illegal for property developers to donate to the NSW branch, but a loophole permits it if the funds are intended to contribute to a federal campaign.

The free trade agreement, which came into force on December 20, 2015, has been criticised by the opposition and unions for threatening Australian jobs – particularly a provision that allows Australian-registered companies with 50 per cent Chinese ownership to bring in Chinese labour to work on infrastructure projects of $150 million or more.

Mr Huang and his associates have donated millions of dollars to the Labor and Liberal parties over recent years, and in 2015 stepped in to pay a legal bill on behalf of NSW Labor reformist and fixer, Senator Sam Dastyari.

Mr Robb was Mr Huang's guest at the Melbourne Cup in 2013, when Mr Huang also presented the trophy. Mr Robb reportedly attended Mr Huang's daughter Carina's wedding in Sydney in January 2016, as did Opposition Leader Bill Shorten.

As trade minister, Mr Robb also attended the "Yuhu 2015 Giving Day" on February 6, 2015, held in part to celebrate Mr Huang's election as President of the Australian Council for the Promotion of Peaceful Reunification of China. That organisation's activities include hosting Chinese government officials in Australia and lobbying against independence movements in Taiwan, Hong Kong and Tibet.

At the time of the donation, Mr Robb was still negotiating the Trans-Pacific Partnership – a 12-country trade deal which does not include China or Taiwan, but that Taiwan had sought to join.

On February 1, the NSW branch of the ALP revealed its biggest donor, Eng Joo Ang, had given $110,000. The next day Mr Eng told media he couldn't recall it and later that he had not made the donation. On February 12, a late return was quietly published on the AEC periodic disclosures as an "update".

Mr Eng is executive vice chairman of the Australian Council for the Promotion of Peaceful Reunification of China.

Mr Robb declined to answer Fairfax Media questions about Bayside Forum's protocols for handling potential conflicts between fundraising sources and his responsibilities as a minister.

"There were absolutely no conflicts of interest," he said.

Mr Huang was contacted for comment but did not respond.

Meanwhile, the Victorian Liberals received $15,000 from the China Australia Media Group, believed to be an arm of the Chinese government. The group has twice been outed for hiring Western journalists at news conferences to ask soft questions of government ministers and officials with the aim of spreading Chinese propaganda.

Chinese property developers have also emerged as generous supporters of political parties. In 2013-14, a pair of Brighton property investors with import-export interests Jianping Fu and Min Zhang, donated $200,000 to the Victorian Labor party. Melbourne-based property developer the Ever Bright Group donated $200,000 to the federal Liberal party and Glen Waverley developer Jiandong Huang donated another $100,000.

Richard Gu's AXF Group, whose development projects include a massive 5500-home project in the city's west, donated $150,000 to the Victorian Labor party. ZJF Investments, a company owned by property developer Zheng Jiefu (who sought refuge in Melbourne after facing embezzlement charges in China), donated $20,000 to Labor's state branch.

Both AXF Group and ZJF failed to make their own donations disclosures to the AEC. Fu Ocean disclosed its $30,000 contribution to the NSW Liberals, but failed to disclose the $50,000 Bayside Forum donation.

The AEC said it was following up outstanding returns.

Governance expert Ken Coghill says foreign donations to Australian political parties should be illegal, as they are in many countries including the United States and Britain.

"The Australian political process ought to be something that is not manipulated or distorted by foreign interests," says the former state Labor MP, now director of the Parliamentary Studies Unit at Monash University.