The EU's former Brexit negotiator, Michel Barnier, said on Wednesday that the reality of Britain's decision to leave the bloc was only now being felt, years after the British 2016 referendum on membership.
Mr Barnier said changes to trade barriers, limits on citizens' movement and work visas were inevitable after Britain finished its transition from the EU on January 1.
"For many people, the real consequences of the referendum are only now starting to sink in," Mr Barnier told an event in Switzerland by video link from Paris.
"The reality, which has become clear for all to see, is that Brexit means recreating trade barriers that had not existed for 47 years."
Exports of food and drink from Britain to the EU plunged by 75.5 per cent in January, Britain's Food and Drink Federation has said, attributing much of the fall to post-Brexit barriers.
The British government says UK-EU trade has been hit by the Covid-19 pandemic and problems with companies adapting to the new Customs rules, which it expects will improve with time.
Mr Barnier said British and European citizens no longer enjoyed free movement in each other's territories.
Musicians must now obtain paperwork for work permits and their equipment in the EU and Britain.
He said Brexit was a lesson for the EU, which must show its 450 million citizens that the 27-state bloc benefited all, and was not the distant, uncaring bureaucracy it was often portrayed to be by Brexit supporters.
Mr Barnier defended his record of negotiating the withdrawal agreement signed in January 2020 and the ensuing trade deal clinched on December 24, 2020.
But he questioned whether he and Britain's chief negotiator, David Frost, were on the same page.
"We managed to conclude an agreement [on trade], although I am still not entirely sure we understood each other all the time," Mr Barnier said.
He attributed that to "a certain view on Europe and sharing national sovereignty".
Mr Frost was regarded as the architect of British Prime Minister Boris Johnson's "hard Brexit" strategy to leave the bloc with a limited trade deal.
Mr Barnier, a French former conservative minister and European Commissioner, committed most of his political life to the deeper integration of European states.