An official from the Environmental Protection Department says the government is looking at cutting the plastic content in designated bags for its planned municipal solid waste charging scheme, a day after the authorities cited higher-than-expected bidding prices for the cancellation of a tender for the rubbish bags.

Under the waste charging plan, residents will have to buy designated plastic bags for the disposal of their garbage.

"Crude oil prices have surged in the past half year, and plastic is made from byproducts of petroleum so its price has also soared, it's something we didn't see coming," said a principal Environmental Protection Officer, Theresa Wu, on an RTHK programme on Tuesday.

Wu explained that bidders had to factor in the uncertainties of future fluctuations in oil prices, rent, inflation and logistical costs and the eventual prices they offered were all higher than the government had expected.

She said the government is testing whether it would be feasible to just have two layers of plastic, instead of three, for the bags.

The official added that the government is looking into shortening the contract period from five years to two to reduce cost uncertainties.

Wu said her department will relaunch the tender as soon as possible and that the process will likely be shorter than last time.

She said her department is still aiming to start the waste charging scheme by the end of next year as planned.