'People go out to have barbeques and often forget to bring rubbish bags,' said Professor Ho Kin-chung, dean of the science and technology school at the Open University of Hong Kong. While his research group thought lack of public recycling facilities, support for recycling facilities, and environmental awareness among young people were the key factors behind the rise in plastic waste, he said waste reduction was a societal problem to be addressed by adults and young people alike.

After plastic bags the next most common rubbish was Styrofoam pieces, plastic sheets/material, plastic bottles, food wrappers and containers, caps and lids, most of which are plastic-based. Plastics are a particular problem for the environment because they stay around for hundreds of years, killing seabirds and turtles as well as collecting as micro-particles in fish and attracting toxins, which can ultimately end up on dinner tables.

Other commonly washed up items were glass bottles, cigarette filters and, for the first time, construction waste. Exactly 2,857 pieces of construction waste were collected - up from 1,237 pieces last year.

About 60 to 80 per cent of marine litter starts out on land, according to Ocean Conservancy's Marine Debris Report 2010.

The Green Council, a non-profit environmental association and co-organiser of the clean-up urged the government to be more vigilant in its enforcement of anti-dumping legislation, and more supportive of recycling efforts in the city.

5m

The number of tonnes of solid waste the city threw into landfills in 2010, according to the Environmental Protection Department