Supermarkets and their suppliers must shoulder more responsibility for reducing food waste, say the authors of a new study claiming that up to half of all food is thrown away.

Retailers’ demand for unrealistically-attractive produce, over-strict sell-by dates, and bogof deals that encouraged shoppers to buy more than they could use were among the factors to blame for the waste, according to a study by the Institution of Mechanical Engineers (IME). Poor agricultural practices and wasteful use of water were also held up as key issues.

The report estimated that between 1.2 and two billion tonnes of food – which is equivalent to half the food produced globally - were squandered every year.

The study - Global Food: Waste Not, Want Not – also stated that it took as much as 50 times more water and 10 times more land to produce 1kg of meat than 1kg of vegetables or rice.

“The amount of food wasted and lost around the world is staggering,” said Tim Fox, IME head of energy and environment. “This is food that could be used to feed the world’s growing population – as well as those in hunger today. It is also an unnecessary waste of land, water and energy resources.”

The western world’s ‘cheap food’ policies had devalued shoppers’ perception of the value of food, said the IME.  “There needs to be a change in mindset,” added an IME spokeswoman. “Consumer and supermarket demand for perfect-looking vegetables, or overbuying of perishable food, sell-by dates versus use-by dates – these are all issues that need to be tackled at all levels and in all sectors.”

And while the IME was “reluctant to point the finger at any one group”, in a response to the report, the British Retail Consortium challenged the idea that promotions were to blame.

“A Government-sponsored report published last year showed that there was no link between promotions and food waste,” said Andrew Opie, BRC director of food and sustainability. “The main method of promotions in this area is cutting the price rather than bogofs. It was supermarkets that lobbied Europe to relax strict marketing rules on fruit and veg, and this has led to an enormous increase in the sale of ‘wonky’ veg as highlighted this Christmas.”

Predictions from the United Nations that the world population will reach 9.5 billion by 2075 have intensified the IME’s calls that the spiralling pressure on land and water needs urgent attention.

“Improvements must be made at all stages in the chain of production, distribution and storage, from the producer/farmer right into the consumer’s home,” concludes the report.

According to Opie, this may already be happening. “We’ll continue to work with growers to use more British produce and cut food waste,” he said.