Labor says expert advice it received when in government raised major concerns over whether dredged sludge should be dumped near the Great Barrier Reef, and accuses the Coalition of “taking an axe” to Australia’s environment since taking office.

Mark Butler, Labor’s environment spokesman, told Guardian Australia that a government-commissioned report placed a “serious question mark” over the proposal to dredge 3m cubic metres of seabed in order to enlarge a coal port at Abbot Point in Queensland.

Butler received the information during his spell as environment minister. He deferred the decision on whether to allow the dredging shortly before Labor lost last year’s election.

The Coalition subsequently approved the dredging and the Great Barrier Reef Marine Park Authority last week gave the go-ahead to dump the dredged material within the boundaries of the world heritage-listed ecosystem.

Butler said the report “cast serious doubt” on reassurances that dumping dredged sand, silt and clay wouldn’t damage coral reefs, dolphins, dugongs and other animals.

“It showed that material was liable to be spread much longer than I had been previously advised, and for much further distances than I was advised,” he said. “From my point of view, the report placed a serious question mark over the proposal. I’m concerned we don’t know what happened to this report. I’m not sure [environment minister] Greg Hunt has answered the questions raised by it.”

Butler said he was “gravely concerned” that Unesco’s world heritage committee would place the Great Barrier Reef on its “in-danger” list when it meets in Doha in June, accusing the government of placing 60,000 tourism jobs and Australia’s international reputation at risk with its “cavalier” attitude towards the reef.

On Thursday, the Great Barrier Reef Marine Park Authority said it tried and failed to persuade North Queensland Bulk Ports to dump the waste on land. Despite this, the authority said it was satisfied that the dredged material, which will be placed 20km from the nearest reef, would not pose a risk to the coral ecosystem.

In a wide-ranging attack on the Coalition’s environmental policies, Butler said the government was guilty of showing a “ruthless” disregard for the nation’s natural assets.

Since gaining power, the Coalition has set about dismantling carbon pricing, including associated bodies such as the Climate Commission and Climate Change Authority, devolving environmental approval powers to state governments in a crusade against “green tape” and scrapping management plans for a huge network of marine parks, claiming that recreational fishers have been unfairly excluded.

Hunt has also exempted Western Australia from federal conservation laws in order to allow the state to cull the protected great white shark and has requested that Unesco remove 74,000 hectares of Tasmanian forest from its world heritage list to allow logging, even though the state’s forestry industry is against the move.

“It’s early days but they are certainly staking a claim for the most environmentally destructive government in Australia’s history,” Butler said. “They have taken an incredibly ruthless approach. It’s absolutely gobsmacking that they’ve taken an axe to Australia’s environment.

“It’s hard to think how they could’ve done any more to damage Australia’s environment in the last four months. They’ve made some extraordinary decisions.

“It’s baffling that the Liberals would want to reignite the forestry war in Tasmania after a long process that involved compromise on everyone’s part. We’ve seen Australia’s reputation on climate change take a terrible hit and we’ve seen an extraordinarily cynical scare campaign over marine parks.

“Without wanting to seem paranoid, it feels like the government wants to erase Labor’s period of government, regardless of policy merit.”

Butler said he saw little prospect of Labor co-operation on any of the government’s environmental policies in the upcoming parliamentary year.

A spokesman for Hunt said the Great Barrier Reef Marine Park Authority had issued a clarification on the report Butler mentioned, tempering its conclusions by stressing that “modelling results should not be used to determine actual dredge material movement or be used to infer where sediment could be dispersed and deposited or its ecological significance”.



The spokesman added: “The information in those reports were considered by the minister. GBRMPA has imposed very strict conditions on the dumping of dredge material.”



The Great Barrier Reef Marine Park Authority said its permit decisions are based on a risk assessment made using analysis from a “wide variety of sources”, the report cited by Butler just one of several pieces of information used for the dumping approval.



“While the report clearly states that the study is not designed to inform individual port decisions, we believe the advances made in modelling methods will be useful in future assessments as it includes more realistic representation of ocean currents than previous modelling,” a spokeswoman for the authority told Guardian Australia.

