Forty-two leading figures in UK farming signed a letter published in The Times on March 5 calling for Britain to remain in the EU.
Launching the 'Farmers for In' campaign, alongside a host of farmers from around the UK, the signatories argue that leaving the EU would be a "risk we cannot afford to take".
Led by former NFU president Sir Peter Kendall, the signatories included former EU Minister Lord Plumb, Sir Jim Paice, Scottish MEP George Lyon and Jilly Greed, co-founder of Ladies in Beef.
The letter argues, "The European single market accounts for 73% of Britain's agri-food exports and gives us access to a market at least twice the size of the US.
"Outside the EU we could keep all or some of this market, but we would have to abide by EU regulations without a say in their formation and pay into the EU budget without receiving EU payments in return. We'd pay, but have no say."
Former NFU president Sir Peter Kendall said: "Being part of the world's biggest trading block is crucial to the future of our farming and food industry."
It allows direct access to 500 million rich consumers, and to 50 other countries via EU free trade agreements.
The group also argued that "environmental threats cross borders, so do the animal and plant diseases which endanger food supplies, and market volatility isn't just a problem for British farmers".
Sir Peter added: "It is pointless trying to tackle these challenges unilaterally, at a country level; only by working together with other member states – with common standards and thresholds – will we give farming the security it needs in today's uncertain landscape.
"I won't pretend the EU is perfect but I'm convinced that as farmers we're stronger, safer and better off inside."
Former Defra farm minister Sir Jim Paice said, "Farmers have had the certainty of the CAP behind them and while it has many faults it is helping them through the current crisis of falling prices.
"Inside the EU we gain from the strength of farmers elsewhere; outside we would be of little importance in a country where few people and even fewer politicians have links with farming. To pretend as some
do that we would get better treatment is cloud cuckoo land."
The letter warns that while Britain would no longer be subject to some EU regulations, exit from the EU would not mean rules would not be replaced by UK ones to address the same issues.
"Farmers need the EU not just for support but for free access to our main export market; leaving Europe would put it all at risk."
Scottish Lib Dem MEP George Lyon, a former NFU Scotland president, said the UK farming industry was much stronger and better off inside the EU.
"The Common Agricultural Policy is far from perfect, but at least it gives us a level playing field on farm support, safety nets at times of crisis, access to markets and the same rules on SPS and marketing.
"An unsupported farming industry would be a disaster for consumers, producers, food processors and manufacturers, with already squeezed farmgate prices plummeting in the struggle to compete with increased volumes of cheap imported food, produced to lower standards of product safety and animal welfare."
But opponents, including Defra farm minister George Eustice, claim that the UK and its farming industry have nothing to fear from leaving the EU.
Eustice outlined his ideas for a 'Plan B' exit from the European Union at last month's NFU conference.
"We would do far better as a country if we ended the supremacy of EU law and actually shaped new, fresh thinking and created policies that would really deliver for our agriculture," said the minister.
Ukip's agriculture spokesman, MEP Stuart Agnew, believes the UK farmers would be better off outside the EU because they would be subject to less red tape.
Agnew has proposed a modified subsidy system with an £80/acre payment to lowland farmers, less pro-rata on uplands, to be capped at £120,000/holding or 1500 acres, if the UK left the EU.
"There will be no more debating on this figure, no greening, no set-aside and no interference in your cropping," Agnew said.
Last month, Defra secretary Liz Truss told the NFU's annual conference in Birmingham that leaving the EU would be "a leap into the dark" that would risk £11bn of UK food and farming exports.
But Defra minister George Eustice told the same conference that leaving the EU would result in an £18bn "Brexit dividend" that will allow the UK to continue supporting agriculture.
