The Government is being urged to launch a campaign promoting how healthy eating can boost the body’s immune system against the threat of coronavirus.

There is considerable evidence that nutritional status crucially affects our immune responses, food policy specialists have said in a letter to Environment Secretary George Eustice and chief executive of Public Health England Duncan Selbie.

The experts say this “vital” consideration has not yet been reflected in the Government’s policy responses to the Covid-19 pandemic.

Clear and well-informed public guidance is required from the government on what is nutritionally necessary and sufficient to maintain UK food security and nutritional appropriateness

Tim Lang, professor of food policy at City, University of London, along with two other academics, wrote: “In addition to current government measures, clear and well-informed public guidance is required from the Government on what is nutritionally necessary and sufficient to maintain UK food security and nutritional appropriateness.

“We therefore urge you to establish and operate new working structures, based on clear principles of equity and health, and with co-ordinated methods of delivery.

“These are needed if the country is to address the numerous and complex quantitative and qualitative difficulties emerging in many parts of the UK food system.

“They are also needed to prepare for further potential disruptions and shortages, if the international and national situation remains critical in the medium term.”

Prof Lang, Professor Erik Millstone of the University of Sussex Business School and Professor Terry Marsden of Cardiff University also point out that most of the UK’s fresh fruit, vegetables and salads come from Spain and Italy – the two European countries with most cases of Covid-19.

They warn that these supplies could diminish rapidly if there were too few people to pick, pack and transport them, and suggest a “volunteer system” could be put in place to ensure supplies.

“UK domestic supplies of fruits and vegetables depend on a sufficient supply of workers, and under conditions of lockdown, and the cessation of cross-border travel, there are very likely to be shortages of workers available, willing and able to produce, pick, pack, process and transport nutritionally vital foods.

“A volunteer system, akin to but improved on what happened in the Second World War, might be desirable to support the food supply, but it needs careful planning to ensure it does not spread Covid-19 infection,” they wrote.

The academics warn that the Government has ceded too much decision-making to the food retailers, writing: “Some retailers have set limits on some aspects of purchasing, but those restrictions are neither uniform nor consistent; nor do they reflect nutritional or immunological considerations.”

They conclude the letter by writing: “As in 1936-40 and in the run-up to a no-deal Brexit, food strains were understood to be highly likely to appear.

“Now is the time to address and resolve these strains, not exacerbate them by undue reliance on a handful of retailers, important though they are, and to ensure that food advice is clear, open and seen to be shaped by the public interest.”

Environment Secretary Mr Eustice said: “Our farmers are doing a fantastic job of feeding the nation during this immensely challenging time.

“I have been speaking with industry about the critically important issue of seasonal workers, who usually come from Europe to pick fruit and vegetables.

“We need to mobilise the British workforce to fill that gap and make sure our excellent fruit and vegetables are on people’s plates over the summer months.

“There are already brilliant recruitment efforts under way by industry and I would encourage as many people as possible to sign up.

“We will also be looking at other ways to make sure farmers have support they need ahead of the busy harvest months, while also keeping workers safe and protected.”