LONDON • Trucks parked along freeways or stuck in gridlocked ports. Food disappearing from supermarket shelves and stocks of medicine under strain. The military on standby, ready to step in to avert a crisis.

For a British public that has often tuned out from the mind-numbing complexities of Britain's withdrawal from the European Union, recent government statements, amplified by raucous newspaper headlines, have finally become comprehensible - and alarming.

For days, talk has swirled about government preparations for a disruptive departure from the EU without any agreement - a scenario that could mean new border checks, log-jammed ports, marooned trucks, and food, drugs and other essential supplies drying up.

The speculation was prompted by a government promise to prepare for all eventualities, including the extreme one of a "no deal" departure from the EU, or Brexit.

But even before the first of around 70 official "no deal" warning documents for businesses and consumers was published, they had started to sound ominously reminiscent of rationing and other preparations during World War II.

On Monday, the government insisted that it had "no plans" to involve the army and was backpedalling over the timing of the 70 warning notices.

Already, however, efforts to prepare for the possibility of a "no-deal" Brexit have backfired by drawing attention to the extreme consequences Britain might face, and to the fact that it might not be able to do much to mitigate them.

And they have angered the very people they were designed to please: hardline supporters of Brexit who had been pressing the government to make "no deal" preparations so the country could threaten to walk away from negotiations with the EU.

"This started off as a way to placate the Brexiteers, and then it turned into something that the Brexiteers hate because the contingency planning sounds so awful," said Professor Anand Menon, who teaches European politics and foreign affairs at King's College London.

Things started to look shaky when the new Brexit Secretary, Mr Dominic Raab, held a meeting with business leaders.

He was reportedly told by Mr Doug Gurr, a senior executive at Amazon, that there could be "civil unrest" within two weeks if Britain quit the bloc with no deal.

Last week, Mr Raab said he would ensure "adequate food supplies" in the event of a "no deal" Brexit, but suggested that this would be the responsibility of the food industry as it would "be wrong to describe it as the government doing the stockpiling".

Britain is vulnerable because it sources 30 per cent of its food from the European Union, plus a further 11 per cent through trade deals negotiated by the bloc, according to a report by the Centre for Food Policy.

The port of Dover, through which thousands of trucks pass every day, has warned that just a two-minute delay in processing time could lead to traffic lines of 27km.

The British government has negotiated a standstill transition period, during which trading ties would remain the same, from the departure date in March next year until December 2020. But this is conditional on a withdrawal agreement that still has to be finalised.

"We are not going to run out of food - this isn't about the return of rationing," said Mr Ian Wright, director-general of the Food and Drink Federation.

"But there could be some shortages and an erosion of choice."

NYTIMES