The Environmental Protection Department on Wednesday said shoppers and retailers will be allowed a one-month grace period over the new plastic bag levy scheme before facing prosecution for flouting the rules.

Lawmakers in October passed a bill to double the levy for plastic bags to HK$1, which will take effect on December 31.

A number of exemptions to the levy will be scrapped. Stores can no longer give out free bags for chilled and frozen food, as well as for food items wholly wrapped in non-airtight packaging, such as bags of apples.

An exemption for unpackaged takeaway food will remain, but will be limited to one bag per order.

Bruno Luk, Deputy Director of Environmental Protection, says authorities will issue warnings in the first month.

"During the first month of grace period... we will give advice or give verbal warnings to anyone who's breaking the law, instead of really prosecuting the retailers. But of course if during the one-month period we found some retailers who are repeat offenders, we may consider launching a prosecution," he said.

Luk added that officials will beef up inspection in the first three months, such as sending "mystery shoppers" to self-checkout counters.

"At the self-checkout counters, they can have one or two staff there just to make sure that customers won't take the plastic bag by themselves. And if they take it and the plastic bag is not exempted one, they [customers] have to properly pay the levy," he said.