The new foreign secretary said that would open up a “fissure” which would change the British public’s attitudes to the EU for a generation.
He called for “more flexibility and creativity” to secure a deal in a speech in Berlin on Monday, after meetings with his German counterpart, Heiko Maas.
Mr Hunt’s visit marks the start of a cabinet tour of European capitals over the summer, as the clock counts down to Brexit day on 29 March 2019.
Prime Minister Theresa May has repeatedly said that “no deal is better than a bad deal”.
Mr Hunt’s visit comes amid reports of plans to stockpile food and close a major motorway in Kent to turn it into a lorry park as emergency contingency measures.
The head of Amazon has also predicted “civil unrest” if ministers fail to secure a deal with Brussels, according to The Times.
Doug Gurr, the British manager for the US online giant, reportedy said it was the worst-case outcome.
Mr Hunt will be looking to reassure other businesses that have spoken out on the progress of negotiations, such as Airbus, on his trip to Germany.
Speaking ahead of the visit, he said: “I will… be clear that our European partners must show much more flexibility and creativity in negotiations if we are to avoid a ‘no deal by accident’ scenario.
He added: “I will reassure my German counterpart that we want to continue to work alongside our European friends and allies, in defence of our shared values.”
Mr Hunt is also expected to discuss the Iran nuclear deal, Paris climate change accord and NATO with Mr Maas.