More than £1bn of food destined for UK supermarkets is thrown away or fed to animals before it leaves farms every year, according to a study highlighting the scale of the country’s waste problem.

Crops rejected by retailers because they do not meet quality standards, fluctuations in demand or problems during storage or packing all contribute to 3.6m tonnes of waste in primary production, more than 10 times the amount thrown away by retailers, says a report by Wrap, the waste-reduction body.

The figure includes 2m tonnes of surplus edible food that does not make it to a retailer or other intended buyer, but is diverted to feed livestock or distributed to charities. The rest is disposed of by being ploughed back into fields, composted or used to create energy.

Peter Maddox, the director of Wrap, said the government-backed body’s detailed study had helped identify key sources of waste and would assist industry with resolving the issue.

Sugar beet is most likely to be thrown away, with 347,000 tonnes wasted every year, according to the most recent data. But poultry accounts for the highest value of waste food at £85m in 2017, according to the report.

“There is huge potential to reduce the amount of surplus and waste by promoting best practice, and that’s where our work is now focused. We want to increase redistribution of surplus food as has happened across the retail sector,” Maddox said.

He said the body had set up a network to connect farmers and small-scale producers to identify new outlets for surplus food, including charities. Wrap is also working with farmers and retailers to improve guidance on setting quality standards, which farmers say are one of the main factors causing waste.

Jack Ward, the chief executive of the British Growers Association, said understanding the scale of the waste problem that puts farmers’ profits under pressure was a positive step forward. “As the sustainability of our food production systems comes under increasing scrutiny, reducing waste at every point in the food supply chain will be an increasing priority,” he said.

Large supermarkets and manufacturers have signed up to efforts to drive down the UK’s annual £20bn food waste bill by committing to halving waste from “farm to fork” by 2030.

Last autumn, Wrap and the food and grocery charity IGD set a series of milestones for businesses to reduce waste at every stage of the supply chain. The annual bill for waste is equivalent to more than £300 for each citizen.