Up to half of the four billion metric tonnes of food produced by the world's farmers every year is wasted.

In its Waste Not, Want Not report, the London Institute of Mechanical Engineers found that between 1.2 billion tonnes and 2 billion tonnes, was wasted due to poor harvesting practices, bad storage and inappropriate transport.

It sounds like a developing world problem until you look at both food retailers and consumers in the Western World.

British retailers reject 30 per cent of food harvested every year, which amounts to 1.6 million tonnes of food, purely because what farmers are producing does not meet their exact size and appearance criteria. There's nothing wrong with the food itself.

Of the more than 3 million tonnes of produce that does reach supermarket shelves in the west, up to half is sold and then thrown away after sitting on shoppers' home shelves. The report puts that wastage down to poor understanding of the best before and use by dates printed on food packaging.

In South East Asia up to 80 per cent of its entire rice production, amounting to about 180 million tonnes, is wasted every year.

Dr William Rolleston, vice president of Federated Farmers, thought it unlikely New Zealand's 4.5 million people wasted anything near the quantities in Europe, but he wasn't surprised by the report's findings.

"Food wastage has always been an issue, it's no surprise," Dr Rolleston said.

The South Canterbury farmer, who chairs the Innovation Committee which reports to the Ministry of Business, Innovation and Employment, put the report's findings down to food becoming too cheap.

"Most of the food wastage occurs at the supermarket and at the consumer's fridge. If food was valued more people are far less likely to throw it out," he said.

"Food has got cheaper and cheaper, it's far less of your weekly income that it used to be, and if you couple that with European subsidies to farmers food is not valued as it should be. It's certainly a strange situation." Dr Rolleston said the European Union's consideration of reducing subsidies was a move in the right direction.

But he said expiry dates encouraged people to throw food out that could still be consumed.

One Waikato supermarket worker, who asked not to be named, said wastage varied depending on department.

He said in some supermarkets stock was damaged in warehouses where birds flew freely and left their droppings on food.

Some fresh lines, such as fresh bread and milk, sometimes had more than half of the units on the shelf wasted while other times they sold out.

"Bread is the worst for wastage because it's got such a short sales date - two days shelf life. We have a lot of issues with over- ordering," he said.

Shoppers often spoiled the supermarket's stock rotation system by manhandling fresh stock, damaging it, and grabbing newer stock behind the older stock at the front of the shelf.

"There's a lot of wastage in the fruit and vegetables department," he said.

Glen Miller, the owner of Mill Street Pak 'n Save in Hamilton, found the report "pretty bloody disappointing".

"I would like to think we are better than most," he said.

His supermarket made an effort to reduce items to clear, rather than throw them out, occasionally buying in items with little shelf life left on them to sell at discounted rates.

"We quite often get offered stuff that's only got a few weeks on it," he said. "We will take two pallets and put a little margin on it. It will be found in warehouses, having been left in a back corner.

"We always reduce stock to clear because it costs money to dump it on weight."

Food that could not be sold was often donated to food banks or sold to pig farmers so it actually wasn't wasted.

Mr Miller thought many shoppers did not understand that best before meant precisely that.

"Some people are convinced at midnight on that day, that's it," Mr Miller said."People think they are going to die. It does mean a lot of that stuff is pulled out."

Louisa Humphry, manager of the Hamilton Combined Christian Foodbank, described the quantum of wastage as "almost a crime".

In 2012 the foodbank distributed $117,000 worth of food to 3,012 families consisting of 5, 880 adults and 4,625 children.

"This year we have seen a little bit of an increase." The food was donated by members of churches from all Christian denominations in Hamilton and from Mill Street Pak 'n Save which also allows shoppers to make cash donations of $2, $5 and $10 at the checkout.

"I guess a lot of people haven't got the time to donate food, but they pick up a tab of $2, $5 or $10." Pak 'n Save shoppers donated about $3200 last year.

"Pak 'n Save have been very good," she said. "Some of the stuff that's out of date they give to us. Sometimes the packaging is damaged."

The foodbank, at 100 Morrinsville Rd, had approached other supermarkets and asked for donations been told they weren't allowed to give away food they couldn't sell, she said.

"I just think that they need to revisit their policies on what they do. Some of it they can't sell but there's nothing wrong with the food. They need to look at their own back doors; there are a lot of needy people that could do with something. Their policy is that they dump it, and there's nothing that we can do. It's so sad. Is it because they think people will wait for that handout and not shop?"

Recipients get budgeting advice and denied further help if they don't attend their next session.

"It's a real problem. People say in our welfare system we shouldn't have needy people but some of them are older people who never ask for anything. We now and again will get a call from the hospital to say an old lady is in with pneumonia because she has turned her electricity off. We will help."

Waikato Federated Farmers president James Houghton said he found throwing out food frustrating but nowhere near half was dumped .

"Any of our food scraps go into a bucket and we feed it to a couple of pigs we have. It gets turned into bacon."

"I hate wasting milk," he said. "So when I am washing out the dairy shed line I make sure the pigs get the milk that's left behind. It's interesting, when you go out to tea, that you see a lot of wasted food on plates."

Mr Houghton thought the best way to reduce food wastage was for people to grow their own vegetables.

"It is really nice," he said. "At the moment every afternoon we get tomatoes for tea although we usually end up giving away a lot."