Greenpeace on Saturday said more than 3,200 pieces of rubbish have been collected in its clean-up operations along two of Hong Kong's riverbanks in the past four months, with 97 percent of it being plastic.

The top items found in the Lam Tsuen and Pui O Rivers were food and beverage packaging, disposable plastic tableware, and shipping materials, the environmental group told RTHK.

Greenpeace campaigner Leanne Tam said microplastics from these sources can enter ecosystems and food chains, potentially affecting human health.

"It easily get into the ecosystem because they are small, maybe eaten by animals. Or even when we drink it or we eat through the food chain, they will enter our blood system or even our brain," she said.

Tam said the government should implement a HK$1 deposit system for beverage bottles, rather than the proposed 10-cent incentive, to better tackle plastic waste.

"The government should add the reduction target on single-use packaging and also the reuse target for the overall package and overall beverage packaging system," she added.

The advocate added that individuals and companies can also play a part by choosing packaging-free items and changing their business models to phase out single-use plastics.