More than half of farms will go bust if Boris Johnson forces through a no-deal Brexit, farmers are warning, as some join the campaign for a fresh referendum.

A deadly cocktail of immediate tariffs, border checks, increased red tape and cheaper food imports from outside the EU will result in the “decimation of UK farming”, a detailed study finds.

“Many industries will suffer, but the industry that would suffer the most serious economic shock will be agriculture,” a former chief economist of the National Farmers Union (NFU) concludes.

The warning comes as the Farmers for a People’s Vote group is unveiled, as the latest arm of the movement demanding a Final Say referendum on the Brexit outcome.

It includes Dr Sean Rickard, the NFU’s ex-chief economist, the founder of an organisation of female farmers called Ladies in Beef and the director of Farmers First, bringing together nearly 3,000 operators from across the UK.

Tariffs in the event of a no-deal Brexit Show all 15 1 /15 Tariffs in the event of a no-deal Brexit Tariffs in the event of a no-deal Brexit Pork There will be tariffs on pork in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Cheese There will be tariffs in place on some cheeses including €22.10/100kg of cheddar, €19.10/100kg of processed cheese and €18.60/100kg on some blue cheeses Getty Tariffs in the event of a no-deal Brexit Milk There will be no tariffs in place on milk Getty Tariffs in the event of a no-deal Brexit Car Parts There will be no tariffs on car parts imported from Europe PA Tariffs in the event of a no-deal Brexit Cars However finished cars will face tariffs of 10.6% Getty Tariffs in the event of a no-deal Brexit Alcoholic drinks There will be no tariffs on alcoholic drinks - except on some rums due to ingredients used in their distilling process Getty Tariffs in the event of a no-deal Brexit Beef There will be tariffs on beef in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Fish There will be no tariffs on many types of fish including cod, haddock, salmon and sea bass Getty Tariffs in the event of a no-deal Brexit Fruit and vegetables There will be no tariffs on almost all fruit and vegetables Getty Tariffs in the event of a no-deal Brexit Chocolate There will be no tariffs on chocolate or other cocoa products Getty Tariffs in the event of a no-deal Brexit Poultry There will be tariffs on poultry in order to protect British farmers Getty Tariffs in the event of a no-deal Brexit Ceramics There will be some tariffs in place on ceramis Getty Tariffs in the event of a no-deal Brexit Steel There will be no tariffs on steel Getty Tariffs in the event of a no-deal Brexit Coal There will be no tariffs on coal Getty Tariffs in the event of a no-deal Brexit Lamb/Mutton There will be tariffs on the meat of sheep in order to protect British farmers Getty

The threat to farming from a crash-out Brexit has already been highlighted by the NFU’s warning of a mass slaughter and burning of sheep, when shut out of the EU market.

The prime minister is considering proposals to buy up excess lamb and beef – at an eye-watering annual cost of £500m – with most likely to be culled in the absence of alternatives.

Now the study warns of the hugely damaging impact of a no deal on farming, because:

* The EU, plus third countries with which it has trade agreements, would immediately slap tariffs on food exports from the UK.

* Tariff-free imports of many agricultural products would have to be offered to non-EU countries as well, including the USA, Brazil and Australia – undermining domestic farming

* It would also be hit by new non-tariff barriers, including administrative costs and border checks to ensure compliance with EU food safety and animal health regulations.

* It would face an effective trade embargo on exports of animal-based products, while the UK and the EU negotiated an agreement.

* The removal of support payments – with only a proportion likely to be covered by Whitehall – and an adverse trading environment will “render the majority of farm businesses unviable”.

Dr Rickard said: “It is impossible to project the exact number of farmers who will go out of business.

“What we do know is that over 40 per cent of them will have no net income if the basic payment is removed.

“If, at the same time, the government removes all tariffs and so depresses prices, these two factors combined will render over 50 per cent of farms in this country unviable.”

And Guto Bebb, a Conservative MP supporting the People’s Vote campaign, said: “Farming is at the very heart of what makes this country great.

“To put that all at risk for the sake of pursuing a disastrous no-deal for which the public haven’t given their consent would be an outrage against democracy.”

On a recent visit to Wales, Mr Johnson failed to explain what help would be given to farmers – even when warned that crashing out of the EU could spark civil unrest.

Instead, he said only: “We have interventions that are aimed to support them and their incomes.”

But the department for the environment, food and rural affairs (Defra) disputed the analysis, saying: “The cash total for farm support will be protected until 2022, even in the event of a no-deal Brexit.

“We will also intervene to provide direct support to boost some sectors in the unlikely event this is required.”