The chairman of Marks and Spencer has laid out the reality of post-Brexit trading saying that goods arriving in the Republic of Ireland have to carry 700 pages of documentation which take eight hours to prepare. Archie Norman told BBC 4's Today programme: "At the moment wagons arriving in the Republic of Ireland have to carry 700 pages of documentation. It takes eight hours to prepare the documentation. Some of the descriptors, particularly of animal product, have to be written in Latin and in a certain typeface."

He said for every sandwich, because they contain butter, it has to have an EU vet certificate. They now employ 13 vets to prepare that paperwork. The deliveries take 30% more driver time.

He admitted the retailer was "at the frontline" of the problems. "We had a business in France exporting into France – we've had to close that because of the customs rules. We have a big business in the Republic of Ireland who very much want to continue but it's proving very, very tough to make it work."

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He added: "We employ 13 vets in Motherwell to prepare at all costs. It takes 30% more driver time. So it's very, very onerous and costs about £30m pounds. At the moment in Northern Ireland we've got what's called an easement so the controls aren't the same but the EU are looking for us to impose comparable controls for Northern Ireland and were that to happen it would mean that quite a lot of products simply wouldn't get to Northern Ireland and what does go there would be very, very costly and Marks and Spencer is a big company – we can make almost anything work, however bureaucratic, but for the small artisan cheesemaker or cake baker and so on it would simply be impossible."

Mr Norman said it currently takes an hour to prepare the documentation to get into Northern Ireland but it's eight hours for what's required to get into Dublin. "The EU proposal is that we should have to do the same background checks to go into Northern Ireland," he added.

"That means that every piece of butter in a sandwich has to have an EU vet certificate. So it's highly bureaucratic and pretty pointless. In all of this you have to understand the purpose of the customs rules is to protect citizens from unsafe food arriving from some far-flung country but our food standards by law are equivalent or higher than those in the EU so there is no risk to safety. There's no purpose to these checks and if they were implemented, the EU proposal to implement them for Northern Ireland, instead of the border controls in Northern Ireland what the commission have asked for is to have every product from Great Britain going into Northern Ireland to be specifically labelled as 'only for consumption in the UK'. That would cost us about £9m a year and of course is impossible for small producers to implement.

"Our preferred approach all along has been to recognise that food standards in the UK and EU are equivalent and probably the highest in the world and therefore we should recognise that and let the product flow not just into Northern Ireland but into France and the Republic.

"The UK Government has been very wary of that because I think there is to some extent or hankering after the idea that there might be some opportunity of Brexit a chance to deviate in the future and the EU of course hasn't been really prepared to contemplate it. So instead the commission have come up with this convoluted set of rules for Northern Ireland."

Mr Norman said food prices were going to go up but stepped back from a warning from the Governor of the Bank of England that rises would be apocalyptic. "I wouldn't use the word 'apocalyptic'. Certainly not for our customers. It wouldn't be surprising to see food price inflation over the course of the running towards 8% or 10% but we don't know that yet. Because it runs through the years some has gone through now but quite a lot still to come.

"Global prices are rising. It's not to do with UK food so much as the effect of freight costs, wheat prices, oil, and energy prices go into almost everything and, as a consequence, all food retailers in the UK are, because we operate on very thin margins, we are reluctantly going to have to allow some food price inflation running to run through the system."