US researchers have revealed Wellington's Oriental Bay has some of the worst levels of plastic pollution in the world.

The revelation comes as a more than 65,000 signature-strong Greenpeace petition is delivered to Parliament calling for an end to single use plastic bags.

Most people wouldn't think of 200,000 plastic fragments - some of them toxic - when they think of Oriental Bay.

"I cried, my mate cried as well," said environment advocate Tina Ngata.

"We actually sat there, and I looked at my friend who's done this research across the world, and the blood had just drained from her face.

"We were like, 'this is the worst we've seen'."

Researcher Marcus Eriksen from the Five Gyres Institute revealed the shocking find.

"I can say, having done this around the world 60,000 miles of sailing in all oceans studying plastic, this is one of the worst beaches I have seen," he said.

Mr Eriksen has been on-board a double-hulled waka travelling down the North Island coast.

"We found more plastic in just those square metres than surveying the entire coast from Napier to here, so we were finding mostly these small pre-production plastic pallets," he said.

Waka Hourua have already done 13 tests across the country trying to work out just how much plastic is in our seas - and the results aren't pretty.

A device trawling behind the waka is used to collect the waste and data.

Wednesday's testing in Wellington Harbour showed where all those pellets in Oriental Bay are coming from.

"Once they're small pieces there's literally no system in the world that can clean them up," Mr Eriksen said.

The sobering findings have come at a time when political pressure is mounting on the Government to come up with a solution.

"I think the strength of this petition the number of New Zealanders who've signed it and just the people who've contacted me, it is an issue New Zealanders care about," said Associate Minister for the Environment Eugenie Sage.

Wednesday's Greenpeace petition has garnered high-profile supporters, such as Helen Clark and Sam Neill, who hope their voices will add weight to a ban on single use plastic bags.

Newshub.