Three more destinations popular with UK holidaymakers could follow Spain, France and the Netherlands onto the coronavirus quarantine list.
Removing the countries from the safe travel exemption would mean anyone returning to the UK would need to stay at home for 14 days.
This weekend France was added to the quarantine list, and it is feared Croatia, Turkey and Greece could be next - according to The Mirror.
Thousands of Brits have already flown to the countries for summer holidays and could face quarantine when they return.
On Sunday, Turkey recorded its highest number of coronavirus cases since June as 1,256 people were confirmed positive and the death toll climbed by 21.
While there are 18.5 infections per 100,000 people, it's a significant surge on the 15.8 recorded last month.
Similarly, Croatia has recorded 162 new infections in the last 24 hours, meaning it has passed the Downing Street's quarantine threshold of 20 cases per 100,000 people in a week.
The number of cases in Croatia has reached 29.3 per 100,000.
The government has, however, asked experts look not only at the infection rate per 100,000 people, but also at the testing rate and reliability of data which each country produces.
Greece could be the next country to have its travel corridor removed after EU figures showed the country's Covid-19 infection rate almost quadrupled in two weeks.
It now appears to be passing the key benchmark, hitting 21.2 in a fortnight, according to the latest figures.
The rate has raced up since sitting at just 6.1 infections per 100,000 people only two weeks ago.
It comes after the Foreign Office advised against all non-essential travel to France following a major case surge there and it was docked from the safe list.
Travellers arriving from France after 4am on Saturday have been required to quarantine for 14 days due to fears over rising numbers of coronavirus cases in the country.
The move came after Boris Johnson said ministers would be “absolutely ruthless” in deciding on whether to impose the self-isolation requirement.
The Netherlands, Monaco, Malta, Turks & Caicos and Aruba were all also added to the quarantine list.
There have been 32.1 Covid-19 cases per 100,000 people in France, compared with 18.5 in the UK.
