Shadow Attorney-General Mark Dreyfus has referred Stuart Robert’s China trip to the Australian Federal Police, asking them to launch an investigation into whether the former minister intended to benefit from the visit.

Mr Robert announced he would step down from the frontbench on Friday, after an internal investigation revealed he had shares in a trust linked to mining company Nimrod Resources, whose chairman Paul Marks is a generous Liberal donor.

Labor had called for Mr Robert to be sacked over the trip in 2014, during which he appeared in a signing ceremony for a mining deal between Nimrod Resources and a Chinese business.

• One promise Malcolm Turnbull surely regrets
• Barnaby Joyce crowned National Party leader
• Labor to restrict negative gearing

In a letter to AFP commissioner Andrew Colvin, Mr Dreyfus argued the “publicly reported facts” about Mr Robert’s trip showed his conduct “may also have involved serious criminality”.

“It is clear that Mr Robert sought to benefit Mr Marks, a significant Liberal donor, but the revelation that Mr Robert himself stood to gain financially through his shareholdings in a company related to Nimrod is even more serious,” Mr Dreyfus wrote.

“The Prime Minister has been careful to say only that this created an ‘impression’ that Mr Robert stood to gain personally from his trip.

“Whether he intended to do so now merits a proper police investigation.”

Mr Dreyfus cited section 142.2 of the criminal code, which deals with the “abuse of public office”.

Mr Robert resigned from his position as Minister for Veteran’s Affairs and Human Services last week, asking Prime Minister Malcolm Turnbull not to consider him in his ministerial reshuffle, confirmed at the weekend.

He had previously said he travelled to China in a personal capacity and that he was confident he did not act inappropriately.

He was one of several ministers dumped from the frontbench in recent months.

Jamie Briggs resigned as Minister for Cities and Built Environment late last year following a late-night incident involving a female public servant in a Hong Kong bar.

Mal Brough also gave up the role of Special Minister of State on Saturday after standing aside last year while the AFP continued its investigation into the James Ashby and Peter Slipper affair.

Mr Turnbull’s new ministry will be sworn in on Thursday.

– ABC