Supermarket bosses and farmers' unions have warned the Government a so-called hard Brexit would put food supplies in the UK at risk.
Migrant workers and tariff-free access to the single market are vital for the industry, Morrisons, Sainsbury's, Marks & Spencer, the NFU and others have warned.
In a letter to The Times, the group also called for assurances that European Union citizens already working permanently in the country would be allowed to remain. The letter has been signed by the NFU in England, Scotland and Wales as well as the Ulster Farmers Union and 71 food businesses with a collective turnover of more than £92 billion, including Dairy Crest, Arla Foods, Weetabix, Wyke Farms and Muller Milk & Ingredients.
The news comes as claims Boris Johnson privately told European Union diplomats he backs freedom of movement were dismissed as a "total lie". Four ambassadors say the Foreign Secretary told them he supported unrestricted migration across the bloc, according to Sky News.
"He did say he was personally in favour of free movement, as it corresponds to his own beliefs," one told the broadcaster. "But he said it wasn't government policy."
Sources dismissed the claims as a "total lie" and insisted he had "never said anything of the sort".
Johnson's spokesman said: "Boris said what he has said many times before - he is pro-immigration but wants to take back control to limit numbers. He did not say he supported freedom of movement and challenges anyone to show proof that he ever said that."
Labour said Prime Minister Theresa May must "get a grip" to end the confusion around Brexit.
Access to seasonal and permanent employees from overseas is "essential" to the food supply chain in the UK, food industry leaders said.
The intervention from the country's largest manufacturing sector heaps more pressure on the Government over the direction its Brexit negotiations will take. European leaders have made clear their opposition to giving Britain concessions on freedom of movement if it wants to remain part of the trading bloc.
The letter states: "For our sector maintaining tariff-free access to the EU single market is a vital priority. It is where 75% of our food exports go, so all our farming and food businesses wish to achieve this outcome.
"The sector needs access to EU and non-EU seasonal and permanent labour, alongside assurances that EU workers already working permanently in the UK are allowed to remain. This access to labour is essential as it underpins the UK food chain's timely delivery of high quality affordable food to consumers. We would urge that the UK Government seeks both these goals as the whole of society and the economy will benefit."
But the Prime Minister indicated curbing immigration was more important than remaining part of the single market when she gave an update on plans for Britain's departure in a speech to Conservatives in October.
Meanwhile, figures released on Thursday will show applications from European citizens to secure their residency status in the country will rise from 37,618 in June 2015 to nearly 100,000 "currently in progress" in early July 2016, according to the Guardian.