The government is spending the summer trying to prove to its backbenchers, the public and the EU that it is genuinely prepared for a “no deal” Brexit, and has plans to manage the massive disruption – most would say chaos – that would ensue if the UK and EU failed to secure a deal.

It might have any number of reasons for doing this. It could be throwing red meat to its backbenchers, to try to show that a no deal hasn’t been ruled out. It could be trying to influence EU negotiators, either by showing that the UK has plans in place, or by suggesting that the negotiators take the blame for the consequences of no deal. It may even be trying to reassure us that it knows what it is doing.

But here’s the problem with any of the above: the government appears to have forgotten to do even the most basic of planning.

As ministers admitted on Tuesday that the UK would be making preparations to ensure an adequate supply of food, medicines and even blood in the event of a no-deal Brexit, the newly installed Brexit secretary, Dominic Raab, revealed the staggering extent of his ignorance as to what that would entail.

“We will look at this issue in the round and make sure that there’s adequate food supplies,” he told the Brexit committee during an extended hearing. “It would be wrong to describe it as the government doing the stockpiling.”

The implication of Raab’s comments – especially combined with comments from other ministers – is that it will be the role of industry to stockpile food, and that that is be something they would be able to do. In an interview yesterday evening Theresa May even said the public should find “reassurance and comfort” in the stockpiling. From those comments, you’d think stockpiling food would be easy.

Dominic Raab revealed ‘the extent of his ignorance’ on food production to the Brexit committee during an extended hearing on Tuesday. Photograph: HO/AFP/Getty Images

It would not. Anyone knowing the very basics of food production – frankly, anyone who has watched an episode of Inside the Factory on the BBC – would know just how difficult it would be for industry to stockpile food. Most UK factories rely on multiple daily deliveries to keep production, which usually runs 24 hours a day, flowing. Within just 18 to 36 hours without deliveries of ingredients, production in almost all of the UK’s food sector (the country’s largest manufacturing sector) would stop.

Factories couldn’t just step up production before the Brexit date and store the surplus, either. They no longer have much space to store their product: the UK’s highly efficient supply chains work on a “just in time” basis – factories have just enough storage space to manage about a day’s worth of deliveries, as do supermarket depots and the warehouses in the back of stores.

Stockpiling more food would mean industry having to buy or lease vast amounts of extra space, at short notice, and probably at great cost. In practical terms, it would ideally have needed to start spending that money months ago – and it would be serious money. Part of the reason people keep less inventory is that it reduces the amount of money you need to operate. If you increase the amount of stock kept in reserve from a few days’ worth to a few weeks’ worth, businesses across the sector would need five to 10 times the working capital they do now.

Who’s going to pay that? Are we going to require an industry that operates on famously thin margins to prepare for this contingency out of its own pocket? What if it refuses? What if it makes these stockpiles, then we cut a deal?

The food sector is a finely tuned machine; a no-deal Brexit would result in it grinding to a halt

This is before we step into many of the extra complexities: food has a habit of going off, for example. Other food takes time to make – nine months for mature cheddar for example. And crops, funnily enough, take time to grow – and can’t be rushed.

The UK food sector, like the UK car industry and much of the high-end goods and services economy, is a finely tuned machine, and the sort of disruption we might see in the event of a no-deal Brexit, such as chaos and delays at the border, would result in it grinding to a halt.

With their comments – presumably meant to assure us that they have a plan, or at least a clue – May and her ministers have shown us instead how woefully under-prepared we are. Brexit is perhaps the most complex thing the UK has attempted in the lifetime of most of us, and it is being run by people who don’t understand the absolute basics. In 2016, these sorts of concerns were constantly dismissed as “Project Fear”. In 2018, we now know that we have good reason to be afraid.

• James Ball is a former Guardian special projects editor, and the author of Post-Truth: How Bullshit Conquered the World