Labor has attempted to suspend proceedings in federal parliament to force embattled minister Stuart Robert to answer questions about his China trip.
"The prime minister needs to show some leadership to this country," shadow attorney-general Mark Dreyfus told parliament on Tuesday.
"This minister has betrayed his duty to this country."
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.
The government has the numbers to quash Labor's move and used its majority in the lower house to gag Mr Dreyfus and manager of opposition business Tony Burke.
"The Turnbull government can't cover up for this minister forever," Mr Burke said.
Cabinet minister Barnaby Joyce said Mr Robert was entitled to a proper hearing and the presumption of innocence.
"I always stand by my colleagues, for all people, I don't want to be part of some lynching group," he told reporters.
"It's not fair on the person, fair on the facts.
"At this point in time, I can't see what has been suggested that Mr Roberts has done that was wrong."
