With the COVID travel list system for international travel predicted to be changed yet again, there are calls for it to be scrapped altogether.
Ministers are predicted to update the traffic light destination system on Thursday, which could see countries moving between the green, amber and red lists.
Portugal is reported to be among the countries expected to be downgraded from green to amber, over fears of rising coronavirus cases in the country.
It saw its highest increase since March in daily cases of COVID infections on Wednesday, with a case rate of around 37 infections per 100,000, compared to 34.5 in the UK.
People returning to the UK from green locations are not required to self-isolate, and only need to take one post-arrival coronavirus test.
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However, holidaymakers who booked trips to Portugal would face a mandatory home quarantine for 10 days and would have to take two post-arrival tests should the country be moved from green to amber.
Brits are not permitted to fly to countries on the red list and anyone returning from those areas would have to pay £1,750 for hotel quarantining.
But Boris Johnson warned on Wednesday that the government will have “no hesitation” over moving countries off the green list if necessary, and said it will “wait and see” what the recommendations of the Joint Biosecurity Centre are before announcing changes to the travel lists.
The prime minister said: “We are going to try and allow people to travel as I know many people want to, but we’ve got to be cautious.
“We’ve got to continue to put countries on the red list, on the amber list, when that is necessary.
“We will have no hesitation in moving countries from the green list to the amber list to the red list if we have to do so.
“The priority is to continue the vaccine rollout to protect the people of this country.”
This morning, Home Office minister Victoria Atkins said the public should “exercise their common sense” about travelling abroad and defended the traffic light system.
Asked on Times Radio whether her department would rather people stayed in the UK, Atkins said: “We’re very, very, very supportive of the traffic light system.
"There are some countries in the world at the moment that because of the variants and the rates of infection are simply too dangerous for us to visit in terms of COVID, and of course they are on the red list.
“We then have the amber list which we very much ask people not to travel to unless there are very particular, very dire consequences they’re having to deal with, such as a dying relative, and then the green list."
While there may be some downgrades, no new destinations will be added to the green travel list, according go the PA news agency.
Summer hotspots such as Spanish and Greek islands plus Malta had hoped to be awarded green status on Thursday.
But no additions are expected to be made amid concerns about rising coronavirus case rates in the UK.
Labour have previously called for the traffic light system to be scrapped altogether, branding it “as secure as a sieve”.
Instead, they argue that there should be a stricter scheme of a blanket quarantine in airport hotels for anyone returning from abroad.
Labour’s shadow home secretary Nick Thomas-Symonds previously said: “The greatest threat we face to our unlocking is a variant from overseas that threatens the efficacy of our vaccines, that’s what we’ve got to do everything we practically can to prevent that outcome from happening.”
Assessments for changes to a country’s placement on the traffic light system are based on a range of factors, including the proportion of a population that has been vaccinated, rates of infection, emerging new variants, and access to reliable scientific data and genomic sequencing.
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