Extreme rainfall cost farmers £1.3 billion last year and will mean a big hike in food prices if it is repeated, industry leaders have warned.
The National Farmers' Union has estimated the exceptional levels of rainfall in 2012 cost the industry £600 million in lost output from poor wheat and potato harvests. It also lost £700m in extra costs such as feeding cattle unable to graze in water-logged fields.
Last year's wheat yields were 15% lower than the five-year average and potato production was just three- quarters of the 2011 levels and the lowest since 1976.
A survey carried out by the Agriculture and Horticulture Development Board suggested 12% less land would be planted this year.
Phil Bicknell, chief economist at the NFU, said 2012 was the sort of year "you expect – you hope – only comes along once in a generation".
Farmers have called for government to provide insurance against extreme weather if it wants to preserve national food security.
The NFU wants the payment to replace European 'Pillar 1' subsidies which pay farmers a set amount for owning land in production – protecting farmers from going out of business during difficult years.
Peter Kendall, NFU president, said: "If the government is determined to move away from Pillar 1, we need a debate about income insurance or protection when we have got years like 2012. It's not the same as producing nuts and bolts in a factory – we can't farm under water or when we don't get any rain."
The NFU said the 2012 "black hole" in farmers' finances was the worst situation for 10-15 years in the industry.
Ian Johnson, NFU South West spokesman, said 2012 was "terrible".
"It's been the worst year that most farmers can ever remember. It's been awful because it started dry, it went wet, it hasn't got dry since, animals are looking for feed which has gone through the roof price-wise. It's getting harder and harder, tougher and tougher with the climate volatility.
"We've got to work together with the food chain to make sure people get a reliable supply of food."
The decline in global production of wheat, maize, dairy products and other foods in 2012 saw consumers hit by steep rises in prices.
Ed Bailey, president of NFU Cymru, told the BBC that livestock feed was also affected.
"The costs haven't fully been realised yet. There's plenty of people with lambs on their farms which haven't sold because they've not fattened because the harvest has been late. There are not able to produce as much milk as they normally would.
"Every sector has been affected by the weather. It's been an exceptional year. Unfortunately as far as weather is concerned it's been an exceptionally bad year.
"Although it's been a bad year, there's still quite a rosy future to the industry.
"Let's hope this is just a one-off and doesn't come to visit us time after time. If it does, unfortunately the price will increase which means extra costs in the shops. Inevitably costs increase as foods become more scarce and there's not a lot we can do about it."