Unvaccinated holidaymakers will be banned from summer staycation sailings operated by P&O Cruises this summer.
Only UK residents who have received both doses of a coronavirus vaccine at least seven days in advance will be permitted onboard, the UK’s largest cruise line said.
Failure to provide proof of the jabs “will result in denial of boarding”, the firm warned.
This is a “strong expressed preference on the part of our guests”, it added.
Other measures introduced due to the pandemic include requiring passengers to wear masks in certain areas of the ship, and making travel insurance mandatory.
There will also be enhanced cleaning regimes and social distancing, while buffet food will be served by staff.
Cruise holidays are traditionally popular with older people, who have been prioritised in the UK’s vaccination programme.
Saga Cruises has previously announced it will require all guests to be vaccinated when it resumes operations in June.
P&O Cruises will operate a series of short breaks on Britannia, while new ship Iona will conduct seven-night itineraries.
Cruises will depart from Southampton between June and September, sailing around the UK’s coastline in search of good weather.
The itineraries do not include stops at any ports, apart from one Britannia sailing which will visit Liverpool.
For her maiden voyage, Iona will anchor off the small Scottish island after which she was named, until sunset.
The Government has advised people to avoid all cruises since July 9, 2020, due to the virus crisis.
But maritime minister Robert Courts told MPs last week that domestic cruises could be permitted from May 17.
P&O Cruises president Paul Ludlow said: “Given recent announcements we have every hope that our guests will be able to enjoy a holiday this summer.
“After the stresses and challenges of the past year everyone certainly deserves a treat and this series of cruises will provide memorable and much-needed UK getaways.
“Whilst there is still uncertainty about holidays abroad this summer, we are delighted to be able to offer our guests the ultimate escape here in the UK with the reassurance that we will take care of everything.
“Also, we really will look at the weather forecast each cruise and aim to take our ships where it is warm and sunny.”
The Government’s Global Travel Taskforce will provide a report to Prime Minister Boris Johnson on April 12 setting out recommendations for how and when foreign holidays could resume.
They could be permitted for people in England from May 17 under the Prime Minister’s road map for easing restrictions.
Turkey announced on Monday that it expects to welcome UK holidaymakers this summer without requiring proof of a coronavirus vaccine or negative test.
Greece will require international tourists to have been vaccinated, had a recent negative Covid-19 test or have coronavirus antibodies, while visitors to Cyprus must have had both doses of a vaccine.