The Croatian state health institute said the rules announced on Wednesday would also apply for visitors from Russia and Cyprus from July 26.
“Due to the worsening of the epidemiological situation in the United Kingdom, Cyprus and Russia, as an additional measure for people arriving from those countries, a negative (COVID-19) test will be required regardless of whether they are vaccinated or have already had the disease,” the statement said.
The country is expecting greater number of visitors from the UK after Croatia was placed on the green watchlist on July 19.
It came as the Balearic Islands were moved from the green list to the amber list.
Croatia’s economy relies heavily on a tourist industry which accounts for almost 20 per cent of gross domestic product (GDP).
On Wednesday Croatia reported 191 new cases of Covid-19. In the last 10 days the number of cases has been rising, most notably in some counties along the Adriatic coast.
Under measures already in place, people arriving from India must be tested, while those arriving from Brazil, South Africa and Tanzania’s Zanzibar archipelago must quarantine for 14 days.
It comes amid reports that travellers arriving into England from green and amber list countries reportedly no longer face such stringent Covid checks.
Border staff will no longer have to check if arrivals have completed a passenger locator form if the computer system fails to find one, The Guardian reported on Tuesday.
A memo seen by the newspaper confirmed electronic border gates “will no longer refer passengers to in-person checks by Border Force officers if a passenger locator form is not found”.
A passenger locator form is used by authorities to trace people who may have come into contact with someone with Covid.
The memo, said to be sent to staff on July 19, also reportedly suggested passengers will not have to provide proof of a negative Covid test before they fly, or confirmation they have booked a follow-up test after they are back in the country.
It comes amid reports of six-hour queues at Heathrow to get through customs due to lengthy Covid checks.
The ISU - the Union for Borders, Immigration and Customs - has since apparently confirmed the Guardian’s reports.
Lucy Moreton, of the ISU trade union, confirmed the reported memo was accurate to the BBC.
“Ultimately this is a political decision,” Ms Moreton said.
“Certainly, it will reduce queue times significantly and hopefully also the level of verbal abuse to which Border Force staff are subject.
“That is welcome to us. The impact on the UK’s Covid security is ultimately a scientific determination.”