LONDON - A 'no-deal' Brexit could snarl cross-Channel trade routes, disrupting supplies of medicines and fresh food while protests spread across Britain, according to a worst-case scenario reluctantly released by the government on Wednesday.

The "Operation Yellowhammer" assumptions, prepared six weeks ago just days after Boris Johnson became prime minister, form the basis of government no-deal planning.

They were released at the demand of lawmakers who accuse Johnson's government of concealing the ruinous impact of leaving without a deal, and could add to the political acrimony as Britain lurches towards its Oct 31 deadline to exit the EU.

The document said public and business readiness for a no-deal exit was likely be low, in part because of political confusion in the run-up to Brexit. Trucks could initially have to wait up to two and a half days to cross the English Channel.

"Certain types of fresh food supply will decrease," it said. "There is a risk that panic buying will cause or exacerbate food supply disruption.... Protests and counter-protests will take place across the UK."

Johnson says Britain will leave on time, with or without a deal. Opposition lawmakers who seized the parliamentary agenda last week have passed a law ordering him to seek a delay unless he agrees a deal with the EU to head off chaos.

Parliament has since been suspended, with courts giving divided rulings about whether Johnson had the right to do so. Johnson says he wants an urgent general election to resolve the impasse. His opponents say they will let him call an election only once the threat of a no-deal exit is taken off the table.

The government said the Operation Yellowhammer document published on Wednesday revealed a worst-case scenario only, and that it had to prepare for all contingencies. Michael Gove, the cabinet minister responsible for no-deal preparations, said the assumptions in the five-page document were being reviewed.

The opposition Labour Party said the documents confirmed the severe risks of a no-deal Brexit, and demanded that the suspended parliament be recalled "to scrutinise these documents and take all steps necessary to stop no deal".