The number of people arriving at a UK port from France has more than halved after Brexit, a ferry firm has said.
Portsmouth ferry port saw 338,000 arrivals in 2019 but only 155,000 in 2022, according to Brittany Ferries.
The firm said "Brexit-related friction" including a need for passports was a major factor, although sailings to and from Ireland, within the European Union, had seen increased business.
The Home Office said the UK's entry rules were relatively generous.
Brittany Ferries said the vast majority of lost visitors were French holidaymakers, including student groups.
Spokesman Nigel Wonnacott said: "We used to have loads of coaches parking outside with happy schoolchildren enjoying Portsmouth, going up to London and we really don't see much of that any more.
"Post-Brexit, French travellers are required to travel [to the UK] with a passport so it's expensive for them to get a passport because it's about 90 euros (£78), and it's also a big administrative burden.
"For Portsmouth, for the surroundings, for UK plc it's the loss of a significant number of potential travellers and all the richness that they bring economically and culturally."
Previously the Tourism Alliance, which represents the British tourism industry, estimated a £875m loss to the UK economy from lost student groups in 2022.
Brittany Ferries said many French visitors had switched to its sailings to Ireland.
Last year saw a 30% increase in passengers travelling on its routes between Ireland, and both France and Spain, compared to 2019, the firm said.
Brittany Ferries operates services from France to Rosslare in Ireland and to Plymouth, Poole and Portsmouth in England.
A Home Office spokesman said the UK's rules were "among the most generous in the world".
The spokesman said visitors from France and other affected countries were told almost a year in advance of the requirement to use a passport from October 2021.
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