Marine species, 90 per cent of which are unique to the region, thrive in unique ecosystems such as the Perth Canyon, a deep-sea channel as vast as America's Grand Canyon, and the 6km-deep Diamantina Fracture Zone, holding life that has yet to be fully discovered.
The proposed park is also home to one-third of the world's whale and dolphin species, and includes breeding and feeding grounds for species such as the Australian sealion, southern right whales and blue whales.
Under the plan, seafloor - or demersal - fishing and gill netting would be banned in "green" marine national park zones, with less restrictive measures covering activities in multiple-use and special-purpose zones.
But the park, and plans linking it to the wider network, are being furiously contested by the fishing industry.
The Opposition is also attacking Government plans, despite the fact that they were originally drawn up by former Prime Minister John Howard's Coalition Administration, which also gave them muscle through the signing of a series of international treaties.
Opening the new proposal for public comment in May, Environment Minister Tony Burke said the nation's marine environment was under long-term pressure from climate change and increasing industry activity.
"Often when we talk about climate change it's about how it affects our land, but climate change is also impacting on our marine environment," he said. "Ocean acidification and rising water temperatures are putting pressure on our marine life."
But environmental groups claim the proposals fall short.
The internet-based lobby group GetUp, starting a campaign yesterday to add pressure on the Government, said the plan to protect the waters off the continent's southwest targeted only two of its 10 marine "hotspots".
"Right now industry groups are doing everything they can to convince the Government that they should be allowed to keep bulldozing our most precious marine hotspots," campaigns director Paul Oosting said.
"Thousands of kilometres of our ocean floor are being devastated by sea-floor trawling."
The new report, prepared by environmental consultancy J Diversity, says marine life is under serious threat from demersal fishing in most of Australia's waters, including trawling, scallop dredging between Victoria and Tasmania, prawn trawling in the tropics and southwestern Australia, and longlining and gillnetting off most of the southern and western coasts.
It says these systems are among Australia's most destructive because of the damage they inflict on the sea floor and the indiscriminate capture of hundreds of species, including threatened and protected ones.
Trawling, especially dredging, ploughs or crushes millions of tonnes of invertebrates such as corals and sponges across areas as vast as the 130,000sq km of the northern prawn fishery, worsened by evidence of further massive damage by gillnets and longlines.
Sharks, many late-maturing and long-living with few offspring, are being reduced to as low as one-third of recommended conservation levels: a number are now on the list of threatened species, or under assessment.
Many are thrown away as bycatch.
Threatened and protected species are also at increasing risk, including sealions - some populations are now at risk of extinction - and dolphins, which one two-year study of trawling off northern WA showed were being caught at the rate of one for every 87 tonnes of fish netted.
"Trawling is one of most indiscriminate fishing methods," Stuart Blanch, director of the Northern Territory Environment Centre, said. "It produces only 2 per cent of wild fish harvest but up to one-third of its bycatch."
Tim Nicol of the WA Conservation Council said the report showed seafloor trawling was as destructive as the clear-felling of forests on land.
"Imagine knocking down a forest to catch the animals that live there," he said. "This is what seafloor trawling does."
