The New Statesman got a free lunch today in London, and we weren't the only ones.

Feeding the 5,000 was an event in Trafalgar Square that aimed to draw attention to the levels of food waste, both in the UK and elsewhere, by giving anyone who turned up a free lunch, a smoothie and as many groceries as they could fit in a bag.

I spoke to the organiser, Tristram Stuart, who wanted to draw public attention to this global problem. "There is enough food here to feed more than 5,000 people," he said, "and all of it would have been wasted had it not come here."

The main reason for this epic wastage is that all of the ingredients -- the apples in the smoothie, the beans in my curry and the bunch of grapes I took home -- are "outgraded", or cosmetically imperfect. In the UK, being "cosmetically imperfect" means that such food won't be sold by the supermarkets, and can be left to rot in the fields. Even if it makes it on to the next link in the food supply chain, it can still go to waste: in the UK, we waste as much as 25 per cent of all the food we buy, or the equivalent of £500 worth of food a year for every British family.

As a result, Stuart and the organisations he worked with, including This is Rubbish and FareShare, are calling on the government to set mandatory targets for reducing the waste. They also demand that supermarkets report the levels of food wasted "at each stage of the supply chain".

The effects of this problem do not stop with the UK, or with the developed world. Matthew Wingate of Save the Children sees a "direct link between the levels of waste in the UK and the life-saving work Save the Children does in some of the poorest parts of the world".

Having recently returned from north-eastern Kenya, where one in every three children is acutely malnourished, Wingate told me that waste impacts "on global climate issues, development aid targets and even individual giving". I asked him how it feels to see this small portion of the food Britain wastes. "To be honest, it feels disgusting," he said. "To return from feeding centres and see skiploads of perfectly edible 'waste' food really does appal me."