Italian Michelin-starred chef Massimo Bottura plans to open two new restaurants in Paris and Naples next year, but wealthy diners are not welcome. The food will be free, made from supermarket scraps and served only to the poor.

Bottura's prestigious restaurant in Modena, northern Italy, charges around 250 euros a head. But in Milan, his Refettorio Ambrosiano feeds the poor, many of them homeless - and now he plans to expand the charitable experiment further.

Housed in an old theatre on the outskirts of the city, the Refettorio cooks free meals with leftovers from shops, following recipes created by Bottura and other famous cooks.

"I never thought these ingredients were waste," he told Reuters.

"I always thought bread crumbs, some overripe tomatoes, brown bananas, they are just opportunities for us. To show what we can do with our creativity."

Bottura started the project in 2015 to reuse leftovers from the eateries of Milan's international Expo. With the support of church foundation Caritas Ambrosiana, the initiative has become a permanent project.

Unlike traditional soup kitchens, guests don't queue. Everyone gets served at the table.

"I call it a restaurant, not a soup kitchen," Bottura said.

This limits the number of daily guests to 96, but Bottura and Caritas say it helps them regain confidence and take back control of their lives.

"Quantity does not define success," said Caritas head Luciano Gualzetti.

"The way you offer your help is the key and it is even more important what your help can trigger in them."

About one-third of the food produced worldwide each year, around 1.3 billion tonnes, is wasted or lost, according to the United Nations Food and Agriculture Organisation.