Britain's food self-sufficiency must be kept above 61 percent to ensure a supply of home-grown food for consumers, the NFU urges the government.
The call comes on the day, 11 August, the country would notionally have run out of food if the public had only eaten British food from 1 January 2019.
The NFU says that farmers must produce more food for a growing population while at the same time delivering on a plan to achieve net zero in agricultural emissions by 2040.
The UK's self-sufficiency has declined over recent years and farmers are calling for politicians to take this fact seriously.
While the UK will never be completely self-sufficient as a country, the NFU says that it is vital that Britain takes its role as a food producer for its growing population.
It comes as experts predict that the population of the country is likely to grow to 73 million people in 20 years time.
British farmers have frequently warned that the UK must not rely on the rest of the world - with varying standards of production - to feed the population.
NFU President Minette Batters said: “When people buy British food they are buying into standards that protect and enhance our natural resources and iconic landscapes.
“They are buying into world-leading standards of animal welfare, and they are buying into the role farmers play in combatting the climate change challenge which is facing us all.
“But there is a lot at stake. This autumn is critical to the future of British farming and with it our ability to feed ourselves.”
Mrs Batters added: “For our part, British farming is entering a new era. We have set our ambition to be net zero by 2040 and with the right food and farming polices in place I believe we have the right roadmap to deliver.
“I hope today acts a wake-up call for all those in power to look at what can be gained and also what is at stake,” she said.