The Consumer Council on Friday called for greater acceptance by the catering trade of customers' own containers when they order takeaways.

It said proactive and flexible cooperation by eateries "is of crucial importance" to promote the container-free practice across Hong Kong.

"Consumers need clear and easy-to-understand guidelines and promotion, complementing the operational procedures of eateries so that [bringing your own containers] can become a natural behaviour," the watchdog said.

"The council hopes that the government and the industry will work together to develop and promote reusable container lending services, so that the public can reduce the reliance on disposable containers and join hands to reduce plastic use at source."

Checks by the council found some restaurants refusing to take boxes from outside for to-go orders.

In August and September, the watchdog's staff members posed as customers and brought reusable food containers to 15 eateries during peak lunch hours on weekdays.

Five of them were part of the government's bring-your-own-containers scheme.

Of the 45 attempts made for the restaurants to accept self-brought containers for takeaways, almost 70 percent were successful, with the watchdog finding eateries taking part in the government initiative more inclined to do so.

The council said four of the 15 eateries refused to accept people's own containers citing food safety and hygiene concerns, with one restaurant employee displaying "a slightly impatient tone" without giving an explanation.

Others said to be accepting such containers were not able to entertain all requests citing practical constraints, such as the time being peak hours and the boxes being too small or dirty, the council added.

"The survey also found that none of the eateries offered discounts for [bringing your own containers], nor did they charge according to the number of disposable containers used on a 'user pays' basis, and some still charged [consumers who brought their own containers] for takeaway packaging," it said.

Hong Kong rolled out the first phase of a ban on single-use plastics in April, with restaurants prohibited from using or selling polystyrene utensils, plastic straws, cutlery and plates. People who fail to comply face fines of up to HK$100,000.

Takeaway plastic lunch boxes and cups will also be prohibited in the second phase of the ban. There's no timetable yet on when that would be put in force.