Fairfax Media understands that, at the time, Thiess John Holland regarded the payment as an acknowledgment of the flexibility of the AWU deal, which was struck by Mr Shorten. Bill Shorten when he was national secretary of the Australian Workers Union. Credit:Andrew De La Rue It's unclear what the union used the money for. Prime Minister Tony Abbott has previously accused the AWU of running a "business model" whose purpose was "ripping off workers to advance its own political position". The deal was hugely favourable to the builder, allowing it to effectively work around the clock by reducing conditions around rostering and weekend work, helping the project finish five months early. It was lauded in a 2006 report by the free enterprise lobby, the Institute of Public Affairs (IPA), which claimed it saved the company tens of millions of dollars. The payment was part of more than $1 million of largely unexplained employer cash flowing into the AWU's Victorian branch between January 2004 and late 2007, when Mr Shorten was either state or federal secretary.

These include almost $200,000 from cardboard manufacturer Visy industries, which at the time was run by Shorten's billionaire friend Richard Pratt, almost $100,000 from aluminum giant Alcoa, and $300,000 from chemical giant Huntsman. The figures are detailed in fine-print in documents lodged with the Australian Electoral Commission as well as documents before the Abbott government's royal commission into union corruption. Fairfax Media understands that some of these amounts include spending on training and payroll deductions that the union will defend if quizzed by the royal commission. Huntsman denied any improper payments had been made and said from 2004 it paid the AWU for an on-site "workplace change facilitator", whose role was to balance the "needs of the unionised workforce and the company".

John Holland declined to comment. A spokesman for Mr Shorten said: "Specific questions about individual contributions from individual companies to the union should be directed to the individual companies or the union". Last week Mr Shorten was called to appear before the royal commission after Fairfax Media revealed the AWU had received $38,228 from Winslow Constructors in 2005 to pay the union dues of 105 of its employees. The Winslow payments continued for a decade, amounting to hundreds of thousands of dollars. Under questioning by the royal commission, current AWU state secretary Ben Davis described the Winslow payments as having "profoundly" weakened the industrial position of the AWU.

Some of payments from Thiess John Holland are listed in union documents lodged with the Australian Electoral Commission, including $134,500 originally described as a "donation" to the AWU. The filing was amended a year later to be describe the money as "other receipt". As a Labor-affiliated union, the AWU is required to disclose some of the payments it receives. Other internal AWU documents, including bank and accounting records, list some of the payments as being for "training" but several large amounts are listed as "service" with "???" beside the entries. Total payments from the construction company into the AWU's state branch bank account under Mr Shorten and his successor Cesar Melhem were $282,308. Another $16,500 was paid into the union's national branch account. Thiess, John Holland and Visy all bought tables to the annual AWU balls in the mid-2000s but they cost only tens of thousands of dollars. Early completion of a major infrastructure project is a rarity in Victoria, where projects are often delayed by industrial issues and other problems. Central to the East Link deal was the elimination of industry conditions routinely demanded by AWU arch-rival the Construction, Forestry, Mining and Energy Union. The deal struck by Mr Shorten halved the number of mandatory rostered days offs, an end to extended "lock down" weekends, and more flexibility to work in hot and wet weather.

At the time, the CFMEU described the deal as a "second rate agreement", and a "shocker" when it came to rostered days off. Originally struck exclusively with the AWU, the CFMEU was later included. But its members were given limited work and its officials had little influence over the project. The IPA report said the reduction in non-working days created a "significant advantage" to the project, allowing work in theory to occur 365 days a year. At the time, Mr Shorten described the workplace deal as a "unique deal" for a "unique project". "The terms deliver long-term, secure, well-paid jobs for our members, while recognising that the whole job should not have to shut down for 26 days every year," he said.

"The agreement provides breakthrough levels of superannuation, parental leave, allowances and penalty rates for the industry." On Wednesday, the union's current secretary Ben Davis told Fairfax Media he would not comment on the period when the union was run by predecessors Mr Shorten and Cesar Melhem. Bill Shorten - Australia's alternative Prime Minister - is one of Australia's best known faces but least defined characters. Fairfax reporters Royce Millar and Ben Schneiders have dug deep to investigate the Opposition Leader's past and present, exploring his character, his politics, his allegiances, and the deals that have put him so close to power. The explosive results of that investigation will be revealed over the next four days.