An inquiry has found that two members of the board which manages Australia's Great Barrier Reef have no conflict of interest despite links to the resources sector, Environment Minister Greg Hunt said Monday.

Hunt in October ordered an independent inquiry into claims that the Great Barrier Reef Marine Park Authority (GBRMPA) had relaxed its stance on industrial development because of ties to the coal and gas industry.

The allegations were contained in an Australian Broadcasting Corporation investigation into links to the resources sector of two of GBRMPA's five board members, Tony Mooney and Jon Grayson.

Mooney is an executive with Guildford Coal and Grayson owns a stake in Gasfields Water and Waste Services.

Hunt said an independent inquiry led by former attorney-general's department secretary Robert Cornall had cleared the men.

"The report finds that allegations of conflict of interest are unfounded," Hunt said.

"The report finds that the two board members have at no time breached their public duty in regard to their position with the Great Barrier Reef Marine Park Authority," he added.

"Mr Cornall recommended that the authority 'take no further action in this matter'."

Both men were at a crucial meeting last year when the GBRMPA board rejected advice from in-house scientists that it oppose port development in areas with the "potential to degrade inshore diversity".

Instead, the board issued a watered-down statement saying such biodiversity impact should be a "key consideration" in port approvals, while calling for further consultations with the mining industry on the issue.

Hunt said Cornall had found Mooney and Grayson had "appropriately disclosed their financial and personal interests".

In Mooney's case the inquiry ruled that his employment with a coal explorer "that does not mine or export coal and has no immediate plans to do so, does not amount to a material personal interest".

Of Grayson, Cornall found his declared personal interests "don't conflict with his public duty".

"The board members' employment and assets, which they declared, aren't considered real or apparent conflict of interest under the Australian Public Service Code of Conduct," said Hunt.

Australia is trying to avert a threat by the UN cultural organisation UNESCO to downgrade the status of the reef as "world heritage in danger".

Hunt said earlier this month that "substantial" progress had been made in meeting UNESCO benchmarks ahead of June's deadline.

Despite threats of a downgrade without action on rampant coastal development and water quality, Australia in December approved a massive coal port expansion in the region and associated dumping of up to three million cubic metres of dredged waste within the reef marine park's boundaries.