LONDON (Reuters) - Britain will face a shortage of fuel, food and medicine if it exits the European Union without a transitional agreement, leaked government documents showed on Sunday.

The newspaper said the forecasts compiled by the cabinet identified the most likely effects of Brexit without an agreement, not the worst-case scenario.

According to the forecasts, 85% of trucks using the main crossings on both banks of the English Channel "may not be ready" to pay French customs duties, which means that unrest in the ports may continue for up to three months before the movement of goods to improve.

The government also believes that restrictions on movement between Northern Ireland and the Republic of Ireland are likely to be imposed, as current plans to avoid expanded inspections will prove unsustainable.

The report, prepared by the Cabinet Office this month, gave a rare glimpse into the government's secret plans to avoid a catastrophic collapse of the country's infrastructure, the newspaper said.

She added that "the file - which has a classification: official sensitive, which means that access to require security clearance - is very important, because it is the most comprehensive assessment of the readiness of Britain to leave the European Union without an agreement."

The opposition is pushing
That coincided with pressure from British lawmakers on Prime Minister Boris Johnson to summon lawmakers from their summer recess, so parliament could debate the Brexit.

More than 100 British lawmakers sent a letter published on Sunday to Johnson, calling for parliament to be convened permanently until October 31, the deadline for the UK to leave the European Union. The summer recess ends on September 3.

"Our country is on the verge of an economic crisis and we are heading towards a Brexit without an agreement," they wrote in their letter, signed by opposition lawmakers and leaders who do not want Britain out of the EU or hope to avoid Brexit without agreement. National emergency must be called to the parliament to convene immediately. "

Opposition Labor Party leader Jeremy Corbin is pushing for a no-confidence vote on Johnson as soon as parliament reconvenes.

If he succeeds in overthrowing Johnson, Corbin hopes to become acting prime minister, demanding a new postponement of Britain's departure from the European Union, avoiding an exit without agreement, and calling for early legislative elections.

Johnson is due this week to tell French President Emmanuel Macron and German Chancellor Angela Merkel that the British parliament cannot stop his country's exit from the European Union.