Two years after clinching a historic free trade deal with Beijing, former trade minister Andrew Robb has become a "high-level economic consultant" with the Chinese company that now operates Darwin Port.

Key points: Andrew Robb appointed to role by chairman Ye Cheng two months ago

Andrew Robb appointed to role by chairman Ye Cheng two months ago Landbridge Group was awarded 99-year lease over Port of Darwin last year

Landbridge Group was awarded 99-year lease over Port of Darwin last year Turnbull Government declines to say when it became aware of appointment

A Landbridge Group company statement obtained by the ABC said Mr Robb was appointed to the role by chairman Ye Cheng at an "auspicious" ceremony two months ago.

The Landbridge Group was awarded a 99-year lease over the Port of Darwin last year in a $506 million deal with the Northern Territory Government that sparked concerns at the highest levels of the Australian Defence Force.

The Landbridge statement from September 2 said "the process of internationalisation of the Landbridge Group and the results achieved had greatly impressed him (Mr Robb)".

"Working for Landbridge Group was a wonderful and pleasing thing, and that he wanted to jointly write a wonderful new chapter together with Landbridge," the statement added.

The company statement, translated for the ABC, also quotes board chairman Ye Cheng as saying that in order for Landbridge to achieve its global goals "it will be necessary to draw on experts such as Mr Andrew Robb who have global vision and global influence".

Mr Robb has been approached for comment on his new role, but the former minister, who is currently overseas, has not yet responded to the ABC.

Ex-ministers banned from lobbying Government for 18 months

The Turnbull Government has declined to say when it became aware of the appointment.

In relation to the Ministerial Standards, Scott Ryan, the Minister Assisting the Cabinet Secretary, reiterated the rules for former frontbenchers.

"It is the responsibility of all former ministers to adhere to the Statement of Ministerial Standards and not take personal advantage of information to which they have had access as a minister where that information is not generally available to the public," Senator Ryan said in a statement.

Former ministers are banned from lobbying the Australian Government for 18 months, meaning Mr Robb would have to wait another year before he can advocate for the Landbridge Group on trade matters.

Mr Robb resigned as trade minister in February, before leaving Parliament at this year's election.

Foreign Minister Julie Bishop defended Mr Robb's decision, telling the ABC he should be allowed to have a post-Parliament career.

"Andrew has said he's aware of the ministerial code of conduct and he'll abide by it," she said.