Environmental groups and scientists across the country will call for immediate action on plastic bags, bottles and microplastics that make up the 34.9 billion pieces of visible plastic in Australian waters, when they front a senate inquiry into marine plastic pollution on Thursday.

The inquiry was called for by Tasmanian Greens Senator Peter Whish-Wilson last year, when he declared Australia's oceans had turned into a "plastic soup".

"I'd like to see a fully co-ordinated national plan where the government shows leadership on investing in research and monitoring the collection of information, this was supposed to happen in 2009," he said.

"I'll be looking to how much funding we have committed to research. There's been a big global spike in studies done, but Australia has contributed almost nothing."