Greenpeace, the Green Earth, Greeners Action and seven other groups surveyed 330 takeaway customers and found them to be supportive of regulating plastic utensils, including plastic lids, food boxes and cups.

But many customers said restaurants had ignored their requests to not provide utensils.

Earlier this month, the green groups visited four fast-food chain branches on Hong Kong Island: Maxims MX, Fairwood, KFC and McDonald's.

They counted the number of plastic utensils provided for breakfast, lunch and dinner and estimated that 500 million pieces are given out each year.

The Environmental Protection Department has launched a two-month public consultation on the regulation of disposable plastic tableware, which will end on September 8.

The government proposed to regulate disposable utensils in two phases.

The first phase will be enforced in 2025, when disposable utensils will be banned for dine-in services and the distribution of utensils such as styrofoam containers, plastic straws, stir sticks, plates, knives and forks will also be prohibited for takeaways.

But plastic cups, food containers and lids will only be included in phase two, which is expected to begin 12 to 18 months after the first phase is launched.

However, 270 million plastic lids, containers and cups have been given out a year, the green groups said.

Leanne Tam Wing-lam, campaigner of Greenpeace, said the 500 million pieces of plastic utensils are only a conservative estimate.

She questioned whether the government's scheme lacked a concrete goal, and urged the government to implement the whole scheme in 2025.

Tam said: "2025 will be the deadline for a complete ban. A policy won't work when it does not have a proper timetable and goal."

The Green Earth and the Chinese University of Hong Kong conducted another survey from February to May.

Among the 336 respondents who had ordered takeaway food in the past year, more than half said they often sought no disposable utensils but the eateries didn't follow their requests.

Green groups also noted that biodegradable utensils are not a good alternative for plastic utensils.

"Biodegradable utensils seem eco-friendly but they aren't," said Edmond Lau Shiu-long, senior officer of Green Earth.

"Those biodegradable utensils actually can't be degraded in landfills," he said.

The groups called for better measures to encourage people to bring their own tableware. Restaurants and supermarkets can also lend reusable tableware to customers.

The groups also suggested the government provide subsidies or incentives to encourage citizens to use reusable utensils.