Plans which would see goods inspectors on the UK border go home from work at 7pm and pare back processing facilities have been blasted as "absolutely crazy" by importers.
The scheme would see almost all checkpoints across England's southern ports shut overnight, and lorries redirected to just one facility in Kent - and has left fresh food carriers up in arms.
The new rules, which came into force on Tuesday, are in place thanks to much-delayed post-Brexit border checks on large quantities of "medium risk" goods, including fresh food.
And while they have been imposed to safeguard the UK against diseases from the continent - including African swine fever - importers have warned they pose risks including severe delays for lorry drivers bringing in perishable goods like food.
The new rules are in place thanks to much-delayed post-Brexit border checks on large quantities of "medium risk" goods
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The government has established a purpose-built site at Sevington in Kent which is set to operate 24/7, and carries capacity to process over 1,200 lorries.
Commercial providers will also be able to carry out in-person checks using official inspectors in Sevington, though many of said inspectors will be unavailable between 7pm and 7am.
The plans will see import vehicles having documentation checked at UK ports before being made to drive on to processing facilities further inland for physical inspections on their goods.
Some drivers, under the new system, could be made to park overnight while border workers are at home until 7am - leaving them unable to deliver stocks to British supermarkets before their deadlines.
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The government has established a purpose-built site at Sevington in Kent which is set to operate 24/7
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And overnight parking has forced worries that lorries carrying valuable goods waiting to be checked could be targeted by thieves.
Nigel Jenney, chief executive of the Fresh Produce Consortium, told the BBC the situation was "absolutely crazy" and would badly affect perishable goods importers.
Jenney said: "Our goods are highly perishable and are delivered on a 'just in time' basis... 95 per cent of all our consignments from Europe arrive in the evening and through the night to be delivered… so that we can enjoy that produce the next day."
Phil Pluck, chief executive of the Cold Chain Federation, called the decision to leave Sevington as the only 24-hour facility "crazy", adding that it was "absolutely stupid when you’ve got lorries coming off at 11pm at night."
Pluck said: "If they're carrying fresh fish, for example, that load will be spoiled and there will be masses of food wastage... It could even mean bankruptcy if the retailer rejects it."
He also took aim at the government, accusing it of not listening to industry concerns and claiming it did not "understand the 24/7 nature of haulage coming over from Europe".
And chaos has reportedly erupted at Sevington already - the Telegraph reported a litany of errors, including computer malfunctions, with one insider saying: "They’ve got the front and back gates open and they’re just waving them all through."
But officials have hit back, insisting there are enough resources for the new checks and claiming commercial customs facilities can extend their opening hours if needed.
Baroness Neville-Rolfe, a Cabinet Office minister, defended the new plans, saying they were essential to defend Britain against imported diseases.
She said: "We have listened to all parts of industry every step of the way and will continue to support them to implement these changes as smoothly as possible."