Ministers have been warned over a new travel traffic light category which could put thousands of holidaymakers at risk of having to endure an enforced stay in hotel quarantine.
Reports have suggested there are plans to introduce an amber watchlist - which could potentially include Italy and Spain.
This will be designed to warn travellers of the possibility that countries with concerning coronavirus data could be put onto the red list at short notice.
There is already a green watchlist to alert holidaymakers that certain destinations could be relegated to the amber list, where anyone not fully vaccinated has to self-isolate for 10 days on their return.
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All travellers entering the UK from green list locations do not have to self-isolate, while there is also an amber-plus list, containing only France at present, which scraps the quarantine exemption for the double-jabbed.
Transport Secretary Grant Shapps, according to the Telegraph, is against the idea of an amber watchlist and would instead like to see travel opened up further.
Ministers are due to meet on Thursday to decide the travel rules that will be in place for most of August.
It comes as the new rules for fully vaccinated visitors coming from the US and European Union came into force earlier this morning meaning they do not need to quarantine on arrival into England.
A spokesman for the Whitehall department said the traffic light system was "kept under regular review" and "based on the latest risk assessment from the Joint Biosecurity Centre", which assesses the public health risk of international travel.
Elsewhere, an autumn booster programme is currently in the works with NHS planning for third jabs to be administered as early as September 6 to help top-up immunity levels.
The Telegraph said vaccines minister Nadhim Zahawi had briefed MPs on the plans, which include the aim of delivering an average of almost 2.5 million third doses a week and carving out an increased role for pharmacies.
A Department of Health spokeswoman said: "The Government is preparing for a booster programme and JCVI (Joint Committee on Vaccination and Immunisation) have published interim advice on who to prioritise for a possible third vaccine from September 2021.
"The booster programme – which would ensure millions of people most vulnerable to Covid-19 will have the protection they have from first and second doses maintained ahead of the winter and against new variants – will be informed by the JCVI’s final advice."
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