If no food is left over at the end of the meal, this will be seen as a sign that the guests are still hungry

The plan follows warnings by experts that Shanghai residents are eating too much - especially at Chinese New Year - and the city is struggling to cope with the amount of refuse created.

The unusual appeal to Shanghai's diners was made by a local branch of the well-known Beijing based chain of roast duck restaurants, Quanjude. Customers who finish their food will get vouchers offering a 10% discount.

'Tradition to blame'

Assistant manager He Ping told local media the restaurant introduced the policy because so many people left their tables strewn with uneaten food.

He said many ate less than half of what they ordered, which was not only wasteful but also harmed the environment by creating excessive amounts of refuse.

Mr He said Chinese tradition was largely to blame. It is customary for one diner to pay for everyone else at the table - and if no food is left over at the end of the meal, this will be seen as a sign that the guests are still hungry, causing a loss of face for the host.

Mr He said in the past staff had often encouraged customers to order less, but had frequently met with angry reactions. He said such attitudes would take time to change - but the restaurant was prepared to accept a fall in revenues in order to reduce waste.

Rubbish piles

The move follows appeals by environmental experts for people to eat less.

According to one local newspaper, the experts say rising living standards have led to a dramatic increase in restaurant waste over recent years, which is adding to pollution of Shanghai's rivers.

The paper, the Wenhui Bao, said the city's refuse collectors had struggled to cope with the amounts of waste produced during the Chinese New Year holiday.

It said their burden had been increased by a new regulation banning farmers from collecting restaurant slops and taking them home to feed their pigs.

The ban is aimed in part at keeping rural vehicles off Shanghai's roads.