Plastic fishing nets, some the size of football fields, are washing up on Australia's northern coastline, slowly killing endangered turtles and creating a "global hotspot" for plastic pollution.

Ben Pearson from World Animal Protection told a national plastic pollution conference that the Gulf of Carpentaria was being afflicted by so-called ghost net pollution.

"These nets can be absolutely massive," Mr Pearson said.

"They can weigh many tonnes and of course they're designed to catch marine animals, which is why they're so deadly.

"The turtles up there that are nesting and breeding are being caught in those nets and in some cases they're dying horrible deaths over many weeks."

Entanglement in ghost nets is one of the most common known causes of turtle deaths in Australia. ( Supplied: Blue the film )

The Gulf of Carpentaria is home to six of the world's seven sea turtle species, and is one of the largest nesting areas in the Indo-Pacific region.

In 2016 Australian authorities removed seven ghost nets weighing more than 29 tonnes from the Timor and Arafura seas.

Discarded nets are being brought in to the region on currents from the Arafura and Timor Seas.

Mr Pearson praised the Indonesian Government for its efforts to combat the problem, which he said is also killing fish, affecting food security and reducing commercial fishing takes by 10 per cent a year.

"In some cases we hear stories that when they catch illegal boats they blow them up as a deterrent," he said.

"That's a very good step but it doesn't eliminate the problem."

Indigenous rangers part of solution

The CSIRO is working with Indigenous rangers from more than 30 communities to clean up the coast, and will conduct an audit in the Gulf of Carpentaria next year to determine the scale of the problem along 3,000 kilometres of remote beaches.

The last study, published in 2013, found at least 5,000 turtles were entangled in more than 8,000 nets.

Indigenous rangers retrieve and analyse ghost nets from the coastline of the Gulf. ( Supplied: Blue the film )

"Clearly there are still a lot of nets up there in the Gulf and we're determined to go up there and try to solve the problem" Mr Pearson said, adding that plastic fishing debris can last for 600 years in the environment.

Ricki Hersburgh from Plastic Oceans Australasia said that marine animals are also ingesting vast amounts of plastic.

The foundation recently produced the documentary A Plastic Ocean and sent a submarine to the sea floor to gather footage of large-scale pollution.

"About eight million tonnes of plastic ends up in the ocean annually" Ms Hersburgh said.

"But those figures may be conservative.