An annual survey by two green groups has suggested more than 4.6 million moon cakes were left over last year - the highest number for seven years.

Food Grace and Green Community recently contacted more than 300 families online, and found that each family on average wasted 1.7 moon cakes in 2021.

William Wong, a senior project officer with Food Grace - an anti-food waste advocacy group - said the figures went up about 60 percent over the year before, as more moon cakes were sold amid a reviving economy.

He said most interviewees said they donated their surplus moon cakes or gave them to relatives and friends, but around 37 percent of respondents admitted throwing them away.

Wong said even more moon cakes could be left over this Mid-Autumn Festival, as he expects sales of the festive food to go up further, partly due to the government's handout of consumption vouchers.

He said people who give moon cakes as gifts should first find out whether the intended recipients actually like them.

"People are giving moon cakes to their friends regardless of their willingness or preference. When we asked people would they like to receive moon cakes this year, the data we received [that said they did] decreased and they were not [as] willing to receive moon cakes as before," he told RTHK.

Wong also called on manufacturers to use simple, recyclable packaging materials, saying more than 80 percent of respondents found moon cakes seriously over packaged.

He also said the authorities should regulate the packaging of such products.