Our Seas Our Future has collated the volume of litter found from 2012 to 2019 on St Kilda, Tomahawk and Smaills beaches and surrounding coastal areas.
Founder Noel Jhinku said the 34,550 litres of rubbish found during the 22 volunteer clean-ups would be only a "fraction" of what was out there.
"The data indicates there’s a consistent trend of rubbish in that area. It doesn’t seem to be improving at all."
There needed to be a "higher-level push" to break the trend.
"There will be agreement that any type of littering is unacceptable, whether it is illegal dumping, accidentally windblown from a lack of or overfilled bins, or deliberate acts of littering."
They found mainly fast food packaging, single-use plastics, bottles, cans, cigarette butts and dumping of household rubbish.
The group wanted the council to make changes to improve the situation.
These included additional bins along John Wilson Ocean Dr, allowing for separation of trash into recyclables such as glass, mixed recyclables and general litter.
It also wanted more regular emptying of bins, the placement of dedicated bottle recycling bins at Ocean Beach and other areas along the Dunedin coastline and litter signage along John Wilson Ocean Dr.
Cameras placed in dumping hot spots, for example Tomahawk Rd, could also act as a deterrent.
"We would like to see a more proactive approach by the relevant local authorities in addressing these ongoing litter issues."
The Dunedin City Council was unable to provide a response to the requests yesterday.