The opposition has asked the Australian federal police to investigate the dumped Liberal minister Stuart Robert over his part in a mining deal during a private trip to China.

The shadow attorney general, Mark Dreyfus, referred the trip to the AFP commissioner, Andrew Colvin, after an investigation by the prime minister’s department secretary found Robert had breached ministerial standards by overseeing the deal while in the country.

Dreyfus told the ABC on Monday the revelation Robert that held shares in a trust linked to the mining company had taken the matter to “a whole new level” and alleged that it was a potential criminal abuse of public office.

“I’ve got great confidence in the Australian federal police’s ability to properly investigate,” he said. “I don’t know what they will find but it’s entirely appropriate that they be asked to investigate. That’s how we maintain standards.”

The resources and energy minister, Josh Frydenberg, told ABC TV the investigations needed to run their course but his colleague had paid a “very high price”.

Dreyfus said Robert had paid the appropriate price.

“He can’t possibly continue as a minister,” he told the ABC.

He said Robert should have resigned last Monday, when it became clear he had breached ministerial standards.

“We had to wait until it could be buried on Friday afternoon.”

Treasurer Scott Morrison dismissed reports that he had argued for the prime minister to keep Robert in the ministry.

“The prime minister and I couldn’t have worked more closely on this,” he told 2GB radio on Monday.

“Those reports of any divisions between us are complete nonsense.”

Morrison admitted Robert had provided “further information” when quizzed by the prime minister’s department secretary Martin Parkinson, who conducted the inquiry into the matter.

“It has ended where it has ended and that is the end of the matter,” he said.