The UK's larders would be bare if the country relied only on home grown produce to feed it this year, farming leaders have said.
Figures from the National Farmers' Union (NFU) show that the UK now produces less than two-thirds of the food it consumes (62%), with the organisation calling for a boost to the nation's self-sufficiency.
By the mid-2040s, the UK's population will have reached 77 million and will only be able to meet around half its needs (53%) from food grown and produced here if action is not taken to improve domestic production, the NFU said.
The farming organisation warned of a perfect storm for British farming, with falling farm-gate prices, a continued downward trend in global markets for household essentials such as milk and supermarkets devaluing food, leaving many farmers in a dire situation.
NFU president Meurig Raymond urged retailers, the Government and the public to back UK farming, saying "If you want great British food tomorrow, then buy great British food today.
"Everybody should be concerned and treat this projected decline in Britain's ability to feed itself as a wake-up call.
"Sustainably increasing production is a challenge I know farmers are up for, but they need to have the conditions which make it possible for them to have a viable future in order to produce Great British food now, tomorrow and in the future."
The NFU is marking the end of self-sufficiency for the year with a Back British Farming Day to highlight the importance of the farming sector to the country.
Mr Raymond said price volatility was being caused by uncertainty in markets, which was not helped by retailers playing "fast and loose on promotions", a lack of investment in the sector and pressure from increased imports.
"Nobody would want a situation where Britain produced less than half the food it needs, we need action now to ensure that the British public - who tell us time and time again that they want to buy British - have that option in the future."
The NFU is calling on the Government to ensure fairer contracts for farmers and implement rules on clear origin labelling and on retailers to show all their products come from farms which have been paid a fair price.
Farmers are also urging the public to ask retailers what they are doing to ensure farmers get a fair price and to keep buying UK produce.