Malcolm Turnbull is seeking advice on whether a minister breached travel guidelines, as Labor ramps up pressure for a full explanation from Stuart Robert.
Federal Labor says the public is owed answers from Malcolm Turnbull and a minister being investigated over a trip to China.
The prime minister has asked the head of his department to determine whether Stuart Robert breached ministerial standards by helping a friend and Liberal Party donor sign a deal in China.
"The Stuart Robert scandal is going to become a test of Malcolm Turnbull's judgment," Opposition Leader Bill Shorten told reporters in Canberra on Tuesday.
Labor wants Mr Robert to explain why he allegedly used his public office for private purposes while assistant defence minister in August 2014 when he flew to Beijing to be at a signing ceremony for Nimrod Resources, a company led by his close friend Paul Marks.
Mr Robert took personal leave, approved by then prime minister Tony Abbott's office, and paid for the trip out of his own pocket.
He has declared a financial interest in companies associated with Mr Marks.
Shadow attorney-general Mark Dreyfus said the ministerial code of conduct was clear.
It says a minister shall not "act as a consultant or adviser to a company business or other interests, whether paid or unpaid, or provide assistance to any such body, except as maybe appropriate in their official capacity as minister".
The Australian Financial Review has reported Mr Robert met China's vice-minister of land and resources, Wang Min, a day after he attended the signing ceremony.
A Chinese government website says the pair discussed Chinese mining investment in Australia.
Mr Shorten told the Labor caucus on Tuesday the opposition would continue to pursue the issues surrounding Mr Robert.
"Yesterday, Malcolm Turnbull gave his full support to Stuart Robert," he said.
"You only need to ask marriage equality campaigners, climate change campaigners and republic campaigners what Malcolm Turnbull's full support means."
