Around 3.5 million British passport holders could be prevented from travelling to some European countries in the event of a no-deal Brexit, according to Which?
This week the FCO warned UK travellers to countries across Europe that their passports may not be valid even if they have 15 months validity left.
Previous government advice said six-months validity would be required.
Which? said of the millions of passport holders affected, between one and one and a half million could try to travel in spring or summer 2019.
But they will be prevented from travelling at the airport, unless they renew their passports.
“If the UK leaves the European Union with no deal, the passport validity rules for travel to most countries in Europe will change from 29 March 2019,” the FCO said.
“Some passports with up to 15 months validity remaining may not be valid for travel.
“Before booking travel, you should check that your passport will meet meet these new rules and find out whether you need to renew it.”
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