Wonky carrots, misshapen potatoes and tonnes of food rejected by supermarkets have been used to give 5,000 people a free curry lunch in Trafalgar Square.
The event organised by charities and farmers aimed to show that a lot of food binned in the UK could be eaten.
Official figures released this week suggest the average British family wastes £680 worth of food a year.
Organisers want people to sign a pledge promising to reduce their food waste and are asking firms to do the same.
"Feeding the 5000" is a partnership between farmers and a group of environmental charities that campaign for better use of surplus food - FareShare, FoodCycle, Love Food Hate Waste and Friends of the Earth.
It was organised by writer Tristram Stuart, who has described the amount of food thrown away in the West as a "global scandal".
"Over the last four decades food prices have come down and food has become more disposable," he said.
"But there are a billion hungry people in the world and demand for more food in the West is contributing to that by pushing up prices elsewhere but then we're throwing a third of it away.
"Personally you may be able to afford to do that but can the planet?".
Mr Stuart said the increasing demand for food production was contributing to deforestation, soil erosion, water depletion and the loss of biodiversity in other parts of the world.
Mayor of London Boris Johnson was on hand to dish up the first bowl of food. He said it was for politicians to take a lead and help change people's opinions.
He said the public had become prejudiced against misshapen veg.
"Mutant food, this stuff is great to eat. It's completely crackers that good healthy stuff like this is being sent to landfill," he said.
Results from the government's Waste & Resources Action Programme (Wrap) show there has been a 13% reduction in household food waste since 2006-7 but figures suggest £12bn worth of food is still wasted by families each year.
Part of the aim of the event was to give people ideas about how to create tasty meals out of leftovers and food they would otherwise throw away.
Chefs including Thomasina Miers, Valentine Warner and Arthur Potts Dawson helped prepare the food to demonstrate what is possible.
Mr Stuart said: "When people get a bowl of food in front of them and it's delicious they automatically ask why would that have been wasted and we have proved our point."
Journalist Rosie Boycott, who runs her own small organic farm and chairs the London Food Board, believes there are lots of creative ways to avoid food waste in our homes.
She said: "Making food go further helps us rediscover the pleasures of home cooking and saves pounds off the weekly food bill.
"Feeding the 5000 brings to life the idea that all food is good food, and every morsel of it is too good to waste."
As well as asking the public to pledge to change their ways, businesses are being asked to sign up to use the "Feeding the 5000 pyramid".
It is made up of promise to reduce as much waste as possible, redistribute surpluses to charity, use what is left as animal feed if possible, recycle through composting and anaerobic digestion and only put food waste in landfill if there is no other option.