Half a million Britons faced a desperate scramble to get home from France at the weekend, while Croatia is expected to be added to the quarantine ‘red list’ within days.
It comes amid mounting anger over the shambolic way the Government has handled travel rules during the pandemic.
Ministers are being urged to replace the disastrous 14-day quarantine system with a ‘game-changer’ virus test at airports, before more countries are put on the red list.
Covid-19 cases are on the rise again in Croatia. Other holiday destinations could also be added if – like Spain and France – they have a sudden second spike in infections that catches travellers unawares.
Croatia is expected to be added to the Government’s quarantine ‘red list’ within days after a rise in cases
An estimated 500,000 raced to return home from France before the 4am Saturday deadline for quarantine that was announced barely 30 hours earlier.
Ministers had previously encouraged people to take holidays to places such as Spain and France as part of a return to normal life.
But hundreds of thousands of travellers were then caught out when the rules changed while they were away, requiring a 14-day quarantine on their return.
Suggestions that Greece and Turkey might be added to the red list have been rejected by travel industry experts. However, such reports have created further confusion, which has hit bookings.
There are also hopes that Portugal, where infection rates are falling, could be removed from the red list this week.

An estimated 500,000 raced to return home from France before the 4am Saturday deadline for quarantine that was announced barely 30 hours earlier
But Croatia has now gone above the UK Government’s quarantine benchmark of 20 cases per 100,000 people in a seven-day period – at 21.5 – and other nations such as Denmark and Switzerland are perilously close.
To avoid further confusion and disruption, travel industry experts are calling for the UK to adopt £50 tests that have been introduced at airports in Iceland.
Advocates of the tests say they would open up international travel, give confidence to holidaymakers and dramatically reduce scarring to the industry and wider economy.
Travellers to Iceland have the option of pre-booking the swab test on arrival instead of going into quarantine for 14 days.

Croatia has now gone above the UK Government’s quarantine benchmark of 20 cases per 100,000 people in a seven-day period – at 21.5
These visitors are required to self-isolate for five days before taking a second test, which is free, at a medical centre. If both are clear, the individual can return to normal life.
The net effect of the system is to reduce total quarantine to less than seven days.
It emerged over the weekend that this exact idea of two tests for people arriving from red list countries had been suggested to the UK Government by experts on the Sage committee two months ago.
Minutes from the scientific advisory group show that it asked Public Health England to consider a double-testing policy.
The plan would have allowed people to finish quarantine within one week. However, no action on testing has been taken.
Heathrow has been running trials where arrivals have the option of paying £150 for two tests.
Travel expert Paul Charles, of the PC Agency, called the current system ‘ridiculous’.
He suggested the Government should adopt the Icelandic testing scheme and subsidise it to bring down the cost to £50.
‘We have to bring this system to the UK as soon as possible,’ he said. ‘We cannot go on with this 14-day quarantine system, which is unworkable and causing anxiety among consumers who are losing money.
‘Adopting this Iceland system here would be a game-changer. It is far better than the damage and scarring being done to the economy by quarantine measures.’
He added: ‘Other countries seem to be far more advanced in dealing with the virus. The £50 tests would save the whole travel sector and allow business and others to freely move around.
‘There are three million jobs at risk in the travel and hospitality industry in the UK alone. Now is the time to change course.’
Mr Charles rejected reports over the weekend that Greece and Turkey are about to be added to the red list.
‘They are nowhere near being added. No chance at all,’ he said.
He said the seven-day figure for Greece is 13.4 infections per 100,000 people, with Turkey at 10.3 – compared with 11.0 here.
Italy appears to be the safest option at the moment with a figure of just 5.5.
Transport Secretary Grant Shapps has questioned the value of airport testing, but suggested the idea is under review.
On Friday, he said: ‘Testing on return is something that we’ve always said we’d keep a very close eye behind the science on those things.’
He said that carrying out a single test – rather than two – would only detect 7 per cent of cases.