Britain’s Farming and Environment Minister, Michael Gove, has told UK farmers they would face rising costs and serious disruption if the country were to leave the EU without a deal.
Gove warned that export tariffs would kick in as well as border inspections that would slow traffic through ports.
He also said a no-deal Brexit would hit smaller farmers and smaller food businesses hardest.
Britain is due to leave the EU on March 29, and the departure agreement that Prime Minister Theresa May has negotiated with Brussels hangs in the balance ahead of a parliamentary vote this month.
Gove was a strong "leaver" during the 2016 referendum campaign on European Union membership, claiming Brexit could bring real gains. But he told the Oxford Farming Conference that any advantages "risk being undermined if we leave the EU without a deal.”
"The turbulence which would be generated by our departure without a deal would be considerable,” he told his audience.
Many British exports reach European markets through the narrow strait between Dover and Calais.
The British government says it is prepared to spend over 118m euros on extra ferries in case of no deal but Gove said there would be other problems to take into account.
“At the moment there are no border inspection posts at Calais. While we hope the French take steps to build capacity there, it is unlikely by the end of March to be generous,” Gove said.
He also pointed to higher haulage costs and significant tariffs on exports such as beef and sheep meat. He added that the government was looking at ways of mitigating these costs but "nobody can be blithe or blase about the real impact on food production of leaving without a deal."
The minister said the deal agreed by Prime Minister Theresa May would provide a 21-month transition period in which current access to EU markets would be maintained.
"If we do secure support for the deal," said Gove, "then we can forge ahead with further reforms which can put Britain in a world-leading position, not just in food production but also in the wise stewardship of our natural assets.
“It (May’s deal) isn’t perfect but let’s not make the perfect the enemy of the good.”
But Michael Gove's opposition counterpart, Labour's Sue Hayman, immediately responded to his speech, calling it "meaningless in the face of Liam Fox’s (Britain's trade secretary) vision of free trade deals that stand to undercut our farming and food standards.
“Labour is calling on the government to support sustainable food production, provide multi-annual payments to farmers and provide a cast iron guarantee that British farming standards will not be undercut by any new trade deals.”