Even a "soft" Brexit could badly impact the food and farming industries.
Its authors claim that this is because there is no Government vision for United Kingdom food or agriculture, yet prices, quality, supply and the environment will all be adversely affected even with a "soft" Brexit.
One of the authors, Prof Tim Lang of City University, described the situation as a "serious policy failure on an unprecedented scale".
Ahead of the departure deadline, there are thousands of pieces of legislation concerning food which require consideration, covering areas such as agriculture and fisheries.
"We are surprised at the failure of the government to address a huge set of issues related to food and agriculture", he said. "Anyone would think they want a drop into the World Trade Organization abyss", he said.
'At least the United Kingdom entered World War Two with emergency plans. No-one has warned the public that a Food Brexit carries real risks of disruption to sources, prices and quality'.
The paper, published by SPRU - the Science Policy Research Unit at the University of Susses - concludes that leaving the European Union poses major risks to consumer interests, public health, businesses and workers in the food sector.
Negotiations over the nature of Britain's divorce from the continent will continue on Monday as Brexit Secretary David Davis travels for talks in Brussels.
The study, by leading food policy specialists Professor Erik Millstone of the University of Sussex, Professor Tim Lang of London's City University and Professor Terry Marsden of Cardiff University, warned the United Kingdom was totally unprepared for "the most complex ever change" to its food supply system.
Mr Marsden said: "The UK's food system already faces unprecedented challenges on environment and jobs - we see real dangers that these are already being dislocated by Brexit uncertainties". But the report criticises ministers for their lack of awareness of the issue: "The silence about the future of United Kingdom food since the Brexit referendum is an astonishing act of political irresponsibility and suggests chaos unless redressed".
Prof Millstone said: "Not only have ministers yet to develop a strategy or make decisions, they have not even grasped the issues about which urgent decisions are needed. Unless things change rapidly, and in line with our recommendations, the United Kingdom will not only have policy chaos, the food system itself will become increasingly chaotic", the report authors said. "When we leave we are determined to benefit from tariff-free trade for our goods that is as frictionless as possible".