EU customs control would kick in the day after no-deal Brexit

It means there would be major disruptions, and queues are expected at the tunnel and ports between the UK and the EU, he said.

"Once the UK will become the third country the day it leaves the EU, therefore the EU customs will apply for all goods coming in from the UK," the French commissioner said.

Moscovici said more than 11,000 goods vehicles per day go through between Dover and Calais or use the Channel Tunnel, although the commissioner acknowledged that not all would be checked.

Member states will have to apply customs rules, and EU countries have invested already in this, Moscovici said, with almost 400 new customs officers recruited in Belgium, 700 in France, 900 more in Germany, and in the Netherlands, and more than 400 in Ireland.

Business needs to prepare as well for a possible no-deal scenario, which was described as "very likely" by EU commission president Jean-Claude Juncker on Wednesday.

Moscovici said some EU countries estimate that there will an increase in customs declaration by 40-50 percent.

Cash flow impact

"This will have a big impact on cash flow of businesses," he said, adding that: "Without an exit agreement, the activity of thousands of European businesses and travellers would be disturbed by the reintroduction of customs checks."

"Every company must prepare to continue trading with the UK," Moscovici said.

Travellers' luggages will also be checked, and they would not be able to bring in British animal products such as cheese, sausages and other delicacies.

Producers would still be able to export these products to the EU if Britain passed laws to comply with EU sanitary rules. Those goods, however, would be subject to import duties.

"I would rather have rigorous check than a health crisis or illegal trafficking," the French commissioner said.

Irish border

Moscovici avoided revealing much on how the EU commission and Ireland plan to police the EU's new external border emerging on the island of Ireland.

"We are working closely and intensively with Ireland to organise these checks in the least disruptive way possible, and as much as possible away from the border," Moscovici said.

The UK and EU pledged to avoid a hard border between Northern Ireland and the Republic of Ireland to uphold the 1998 peace agreement, and the EU is also keen on protecting the integrity of its single market.

There would be no checks on goods coming from Ireland to mainland EU.