On one evening Mr Rudd left his hotel to meet with Mr Chau, accompanied only by one of his staff members, rather than an official from DFAT as is customary.

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The meeting with Mr Chau, which was not part of the official schedule, came as Mr Rudd was mounting his guerrilla campaign to undermine Prime Minister Julia Gillard and retake the ALP leadership. It has been suggested Mr Rudd was seeking Mr Chau’s continued support, as the billionaire property developer had been a major donor to both sides of politics.

Mr Rudd's office has previously told Fairfax Media in comments, unreported until now, that there was nothing unusual about it.

“When Ministers are travelling, such personal meetings regularly occur,” Mr Rudd’s office said.

"To imply ... that Mr Rudd sought to 'slip [diplomatic] minders is false. If anybody had that impression, then they are mistaken.

“Detailed liaison between Consulate officials and Mr Rudd's private staff about the content of his public program and personal engagements were routinely resolved at the staff level without Mr Rudd's engagement.”

Mr Rudd could not be contacted for fresh comment before deadline. Fairfax Media does not suggest that Mr Rudd, who was accompanied by a senior political staffer, did anything improper in meeting Mr Chau.

In his speech of Tuesday night Mr Hastie also used parliamentary privilege to allege Mr Chau had funded a $US200,000 ($263,000) bribe to a senior United Nations official.

Mr Hastie and Prime Minister Malcolm Turnbull came under fire over the revelations in parliament on Wednesday, as opposition leader Bill Shorten sought to exploit apparent divisions within the Liberal Party.

One diplomat with knowledge of the incident said while it was not necessarily a breach of protocol, which was "pretty flexible" in most circumstances, Mr Rudd's behaviour was “extreme”.

“It was ... extraordinary behaviour and given that, you need to ask why was it necessary?” said the source.

The person said Mr Rudd’s office only informed Australian diplomats in China at the “very last minute” that he would be visiting on his way back from meetings in Norway.

The visit to the southern city of Guangzhou was also unusual as it happened over a weekend and did not include a trip to the capital Beijing.

Another source said Mr Rudd’s meeting with Mr Chau caused serious concerns within DFAT and it was discussed at length, once they were made aware of it.

His failure to alert DFAT staff was seen within the Department as a substantial; departure from normal procedure, the person said.

Mr Chau, an Australian citizen, has given more than $4 million to both sides of politics since 2004 and has a Frank Gehry-designed building named after him at the University of Technology Sydney. He has donated $45 million to Australian universities, according to Mr Hastie.

Mr Chau's lawyers issued a statement late on Wednesday saying he was "very disappointed" that Mr Hastie had used parliamentary privilege "to repeat old claims and attack his reputation just weeks before some of these matters are tested in court".

"Our client has not been charged with any offence, which makes Mr Hastie's attack all the more extraordinary," Mr Chau’s lawyer said.

The response to Mr Hastie's speech in political and media circles has been confused by misreporting about the source of his information. The confirmation that Mr Chau was the person described as "co-conspirator 3" in a New York bribery case was provided to Mr Hastie by a US prosecutor in a non-classified briefing, rather than the FBI as has been reported in many outlets. The fact that Mr Chau was one of the unindicted and unnamed co-conspirators in the case had also been previously reported previously on many occasions and is detailed in court documents.

Senior US officials with knowledge of the case were either unconcerned by, or supportive of, Mr Hastie's speech and are understood to also be dismissive of allegations in a Sydney newspaper suggesting otherwise.

Mr Chau has extensive property and other business interest in Australia and China.

The 69-year-old is ranked 45th on this year’s Financial Review Rich List, which will be published on Friday, with an estimated wealth of $1.63 billion.

He purchased James Packer’s former Sydney residence for a record $70 million in 2015.
In addition his wife, So Chun Chau, and daughter, Winky Chau reportedly paid $31.8 million for a Darling Point mansion in February, a record for a non-waterfront property in the exclusive Sydney suburb.