A no-deal Brexit would "inevitably disrupt" fresh food supplies in Britain because delays at ports would throw just-in-time deliveries into chaos, the chief executive of supermarket group Sainsbury's said.

Mike Coupe said the October 31 Brexit date could not come at a worst time for supermarkets because warehouses were already full with Christmas produce and more of the supply of fresh salad had switched to southern Europe.

British Prime Minister Boris Johnson said yesterday that the government had been "massively accelerating" its preparations.

He said the country would "be ready" if Britain left the EU without a deal at the end of October.

Asked if plans were in place that meant disruption to food supplies could be ruled out, Coupe said : "I disagree with that wholeheartedly, the reality is there will inevitably be disruption, simply because we've never done this before."

Other supermarket bosses said this week that Britain was unlikely to run out of essentials like toilet paper in the event of a no-deal Brexit but some fresh fruit and vegetables could be in short supply and prices might rise. 

Senior retail figures have also said that the government's demand for supermarkets to prepare for a no-deal Brexit by stockpiling food was stoking anger in the industry.

Supermarket bosses said they should not be blamed if people can't find everything they want on the shelves.