Leaving the European Union without a deal at the end of October would be more difficult than the original March deadline, the Tesco CEO said today.
Dave Lewis said this was due to less storage capacity for stockpiling in the run up to Christmas.
Retailers, manufacturers and pharmaceutical groups built up stocks of goods and parts in the run up to Britain's original March 29 deadline to leave the bloc.
But that date that has since been extended to October 31 after Prime Minister Theresa May failed to get her deal through parliament.
"It will be more difficult to do that in October, that's for sure, because all of the network will be full of things getting ready for Christmas so there will be less capacity," Dave Lewis said today.
Mr Lewis told his company's annual general meeting in June that sourcing fresh food would also be a major issue as Tesco imports about 50% of the fresh food it sells.
"Empty shelves depends on what no-deal means," he said.
"If there's a problem at the border, if there's a problem with tariffs then there could be interruption," he said today.
"If as part of no deal there is no tariff, there is no problem, we could be absolutely fine," he added.