Coronavirus could make disruption at the border caused by Brexit worse, the government has warned.

A “reasonable worse case scenario” document published by Michael Gove warns of queues of 7,000 lorries in Kent if not enough businesses prepare for border checks and requirements following the end of the transition period on December 31.

And a Covid-19 winter spike could make the situation worse if it leads to “absenteeism among port or border staff” in Dover or Calais, or if social distancing measures create extra friction.

The document however notes that a surge in infections may also suppress demand for freight Channel crossings and “limit the extent of traffic disruption”.

Gove also confirmed controversial plans for a “Kent access permit” which lorry drivers will have to hold to get into the county – an attempt to reduce traffic that critics say amounts to a de facto border inside England.

He published the document while warning that not enough firms are prepared for the UK leaving the EU single market, which allows seamless trade with the continent, at the end of the year.

“Our survey evidence indicates while 78% of businesses have taken steps, just 24% believe they are fully ready,” he told the Commons.

“Indeed, 43% of businesses actually believe the transition period will be extended even though the deadline for any extension has now long passed and the date we leave the single market and customs union is fixed in law and supported across this House.”

The document’s worst case scenario estimates that 30-50% of lorries will not be ready for extra border checks and requirements, leading to a 60-80% reduction in the normal levels of Channel crossings.

“This could lead to maximum queues of ~7,000 port bound trucks in Kent and associated maximum delays of up to two days,” the document says.

The problems may start small in early January but there is an expectation of “sustained disruption to worsen over the first two weeks as freight demand builds”.

The government expects disruption to begin tailing off over the first three months of 2021 as more firms get their lorries ready with the correct paperwork for the border.

But there is a warning that EU passport control could continue to cause disruption “until the French relax checks or add more capacity to undertake checks”, the document states.

Meanwhile, Gove said the government had made “progress” in getting Brussels to grant it the automatic right to export food to the EU after the transition ends.

The UK had warned that without so-called “third country listing”, trade of food between Great Britain and Northern Ireland, which will follow many EU rules so it can keep an invisible border with the Republic, could have been disrupted.

“The reluctance or the slow pace of granting third country status for food exports to the UK has been concerning but thanks to the prime minister drawing attention to this issue, progress has been made,” Gove said.

Shadow cabinet minister Rachel Reeves said people must assume that these worst-case scenarios over the post-Brexit situation “will play out quite soon”.

She said: “The news today that there could soon be tailbacks of 7,000 lorries is quite extraordinary.

“I know the government has said that they are committed to building new infrastructure, but I didn’t realise it meant concreting over the Garden of England.

“Today’s warnings are based on a reasonable worst-case scenario, but given we have a reasonable worst-case government, we have to assume that these scenarios will play out quite soon.”

Reeves added: “Why aren’t the essential prerequisites for a smooth transition not already here?

“It is all well and good to tell businesses to act now, but without the systems in place, frankly, it is like telling me to bake a cake but forgetting to turn the oven on.”