Britons heading to France and other EU countries were warned by the Foreign Office that they will be fingerprinted and face border queues due to Brexit.
They will also have their photograph taken before they leave the UK, or on arrival in another European country.
Ministers said there could be longer queues at Dover, the Eurostar terminal at St Pancras in London, and Eurotunnel at Folkestone in Kent.
The new requirements and expected delays are due to a new digital border system being introduced by the European Union and some other countries.
In an update on Thursday to travel advice to France, the Foreign Office said: “From November 2024, the new EU Entry/Exit System (EES) will start for all non-EU nationals, including British nationals, travelling in or out of the Schengen area.
“The Schengen area is made up of 29 European countries, 25 of which are EU Member States.
“The EES is a digital border system which registers non-EU visitors travelling into the Schengen area instead of stamping their passports.”
It explained further: “You will need to have your fingerprints and your photo taken when entering the Schengen area.
“If you enter the Schengen area through Dover, Eurotunnel at Folkestone or St Pancras International, your fingerprints and photo will be taken before you leave the UK.
“You will also need to provide either your fingerprint or photo on exit.
“You may experience longer queues at borders when the new system starts.”
The same warning was posted on travel advice to other EU nations including Germany.
If Britain had remained in the EU, people heading to the Continent would not be subject to the new border rules for the European Union.
Economists have also warned that Brexit has dealt a multi-billion pound blow to UK trade.
Brexiteers trumpeted ahead of the 2016 referendum on quitting the European bloc that doing so would allow Britain to take back control of its borders.
However, since quitting the EU, net migration to the UK hit a record 675,000 in 2022.
Tens of thousands of people are also crossing the Channel in “small boats” to reach the UK, with some dying in drowning tragedies.
France has been accused of failing to do enough to stop often unseaworthy inflatable boats, overcrowded with men, women and children, from leaving its shores.
Some experts say Britain should introduce ID cards, to make it harder for people to work illegally in the country, as part of a plan to stop so many migrants risking their lives by trying to cross the Channel in the boats run by human trafficking gangs.
