Embattled Turnbull government minister Stuart Robert has fresh questions to answer after revelations he met with a Chinese government minister during his secretive 2014 trip to Beijing, the opposition says.
Mr Robert's frontbench future is under a cloud for his role at a signing ceremony for a mining deal between his close friend and major Liberal Party donor Paul Marks and Chinese government-owned company Minmetals.
Labor has accused Mr Robert, who was then assistant defence minister, of a conflict of interest and breaching ministerial guidelines by misusing his public office. Mr Robert owns shares in Mr Mark's other companies.
Now Human Services Minister, Mr Robert claims he was in Beijing in a "personal capacity" but a Minmetals press release says he was there on behalf of the Australian government and made a speech.
Prime Minister Malcolm Turnbull has ordered his department to investigate whether Mr Robert acted improperly but there are now revelations Mr Robert also had a meeting with a senior Chinese government minister on the trip.
The Australian Financial Review has revealed Mr Robert met with China's vice-minister of land and resources, Wang Min, a day after he attended a signing ceremony.
A Chinese government website says Mr Robert and Mr Wang discussed Chinese mining investment in Australia.
Defence Minister Marise Payne backed Mr Robert on Tuesday.
"I have complete confidence in the minister and of course the matter has been referred to the Secretary of the Department of Prime Minister and Cabinet," she said.
But shadow Attorney-General Mark Dreyfus said Mr Robert must explain himself.
"He's got to now make a full statement as to what it was he was doing in Beijing. It can't be both a trip for private purposes and a trip on which he met with a vice-minister in the Chinese government," Mr Dreyfus told reporters.
He also called on Mr Turnbull to show leadership on the issue: "Running for cover behind a departmental inquiry is simply not good enough."
During a Senate estimates hearing on Monday night, a Department of Prime Minister and Cabinet official revealed Mr Turnbull only requested the investigation at 1.58pm - just two minutes before a fiery question time where the saga featured prominently.
Earlier that night, Mr Turnbull's office distributed a letter Mr Robert wrote to Mr Turnbull. In the letter, the besieged minister noted he was "confident that I have not acted inappropriately" but still asked for the probe by the PM&C.
The official could not tell the estimates hearing how long the inquiry would take.
Opposition Leader Bill Shorten says it isn't looking good for Mr Robert.
"There's a lot of explanation required about what this fellow was doing in China and all the detail of what's gone on," he told ABC radio.
Mr Robert describes himself a "close personal friend" of Mr Marks, who has donated $2 million to the Liberal Party in recent years.
The scandal comes only weeks after Mr Turnbull lost two ministers - Jamie Briggs and Mal Brough - to scandal.