The uneasy alliance between the four UK nations over quarantine for returning travellers has fallen apart, with England, Wales and Scotland now operating conflicting policies.
The transport secretary, Grant Shapps, said there will be no changes to England’s quarantine list.
He tweeted: “We continue to keep the Travel Corridor list under constant review & won’t hesitate to remove countries if needed. However, there are no English additions or removals today.”
However, Wales has imposed almost immediate quarantine on Portugal, Gibraltar and six Greek islands: Antiparos, Crete, Lesbos, Mykonos, Paros and Zante (also known as Zakynthos).
Self-isolation for two weeks awaits Welsh holidaymakers who do not return by 4am on Friday. The usual deadline for England is 4am on Saturday.
Residents of Wales who arrive at English airports, such as Bristol, Birmingham or Manchester, must follow the stipulations of the Welsh government.
Scotland has also gone against the UK government’s decision and imposed quarantine for arrivals from the whole of Portugal from 4am on Saturday.
The justice secretary, Humza Yousaf, tweeted: “This week’s data shows increase in test positivity & cases per 100k in Portugal.”
On Tuesday evening, the government in Edinburgh ruled that arrivals in Scotland from Greece must self-isolate for 14 days.
To decide if a country is high or low risk, the UK government and the Joint Biosecurity Centre focus on the number of new cases per 100,000 citizens in a seven-day period.
When that figure reaches 20, the nation is normally deemed to be dangerous – though not so risky that holidaymakers must come home immediately.
The UK is currently at 15 on that measure, with Portugal on 23.
Many of the estimated 20,000 British tourists currently in Portugal who have been following, with increasing concern, the data used by the government to decide each country’s status, bought up tickets – especially from Faro airport, which serves the popular Algarve coast.
The last seat on a Jet2 flight from Faro to Manchester on Friday afternoon sold for £556.
Paul Charles, chief executive of The PC Agency travel consultancy, said: “In a clear sign of how ill-thought-out the policy is, the government is now ignoring its own quarantine criteria.
“With countries such as the Netherlands and Austria rated with fewer infections in their populations than Portugal, then we’re all looking forward to seeing these countries now taken off the quarantine list.
“Only testing and more testing is the solution to walking the tricky tightrope between health and economic priorities. With over 30 other countries worldwide testing at airports, it’s still not clear why the UK is waiting to invest in such infrastructure.”
Gibraltar, which has had a rate at least three times higher than Portugal for at least two weeks, has also retained its quarantine exemption.
Earlier, the health secretary, Matt Hancock, rejected industry pleas for a testing regime at airports to reduce the current quarantine, saying, “It doesn’t clinically work”.