Transport Secretary Grant Shapps said others will have to isolate themselves for 14 days when they return from Croatia, Austria and Trinidad and Tobago.
Adjustments apply to arrivals after 04:00 BST on Saturday.
Meanwhile, the Scottish government has added Switzerland to its list of countries that require quarantine.
The Portuguese government called the adjustments “useful for all travelling between Portugal and the United Kingdom.”
He said the resolution is “a test of the clever end results of intense bilateral work” and “made it clear that the scenario in the country has been under control.”
But the customer’s organization Which?said that it is likely that the replacement of the rule for Portugal “arrives too late due to the assistance of many troubled holiday companies” and asked the travel industry.
The most recent quarantine list updates come after thousands of British tourists made a last-minute effort to return from France last weekend, before quarantine measures came into effect.
Around 20,000 Britons are believed to be in Croatia lately.
Responding to changes, which one? The editor, Rory Boland, said the government “has now made it transparent that countries can be removed or added to the list of brokers at any time.”
He said politics makes it “too risky” for quarantiners to travel.
But he added that tourists who want to stick to the government’s recommendation and avoid the non-essentials for specific countries are “having increasing difficulty requesting a refund.”
Boland also called on the government to provide “urgent” to the travel industry, adding: “The incorporation of Portugal will probably be too long due to the assistance of many troubled holiday companies on the brink of collapse, as summer travel has already done..has been canceled.”
The Tucker family, from Cambridge, was in a beachfront café on the Croatian island of Solta, opposite Split, when they learned that they would have to quarantine on their return to the UK.
“We already canceled one in Barcelona because of quarantine rules,” said Mother Luzita, 50, a nursery assistant.
“We wanted to come to Croatia, so we looked at the infection rates and they looked very low.”
He said it was smart for the government to act with a decision, but he warned that there were other options.
“Why not [do] virus tests at the airport when we return to the UK? And public delivery to get home can be a risk.”
Diane Barwick was in the Croatian city of Zadar for her daughter’s stopover after canceling a planned trip to France when that country was removed from the exemption list.
She told BBC News: “My daughter got married here in May. I haven’t noticed her in almost a year and I’ve had 3 flights canceled this year.”
Unlike many other British visitors in Croatia, she had responded to rumors that the country was about to be removed from the waiver list by booking another return flight early.
This means that you will be able to return home before the deadline and repaint in the retail sector.
“If you are in France, you can take the boat or the Eurostar.Here, it’s just a flight. I have to travel 3 hours to get to the airport in Croatia,” he said.
The Ministry of Transport urged citizens of Croatia, Trinidad and Tobago and Austria to adhere to local regulations and the Ministry of Foreign Affairs online page for more information.
In a statement, he suggested that employers “understand those who return from those destinations and will now have to isolate themselves.”
But young people who are currently on holiday in those 3 countries will now miss the start of the new school term in England, Wales and Northern Ireland, unless their parents can take them home until 04:00 BST on Saturday.
People who do not isolate themselves when they can be fined up to 1,000 euros in England, Wales and Northern Ireland, in Scotland the fine is 480 euros and up to 5,000 euros for repeat offenders.
BBC Balkan correspondent Guy De Launey said only a small number of direct flights from Croatia had to succeed in the UK before saturday’s 04:00 BST deadline.
The United Kingdom imposed mandatory 14-day quarantine for arrivals in early June.
But the following month, the 4 British countries revealed lists of “travel brokers”, detailing the countries that were exempt from the rule.
Since then, it has regularly updated this list, adding and cutting countries based on their coronavirus infection rates and comparison with the UK.
In July, the Portuguese government expressed its “regret” for the UK’s resolve to continue excluding it from the safe list.
The country’s foreign minister had said in the past that he hoped that an “air bridge” between the UK and Portugal could be secured until the end of June.
The UK supplies the largest number of foreign tourists to Portugal, with more than two million tourists a year.
The Algarve coast is the most popular destination, with 1.2 million Britons last year.
Travel expert Simon Calder tweeted that the fare for flights from Manchester to Faro on Saturday morning had 50 to 98 euros in 30 minutes.
“This is the time to ebook on this end-of-summer vacation, even if the costs are already soaring,” he said.
According to the Ministry of Transport, weekly coronavirus instances are in Croatia, Austria, Trinidad and Tobago as follows:
Have you been affected by the new quarantine measures? Share your reports by sending an email to [email protected].
If you would like to speak to a BBC journalist, please include a contact number.You can also contact us in the following ways:
If you are reading this page and cannot see the form, you will want to log in to the cell edition of the BBC online page to send your inquiry or comment or you can send us an email [email protected], age and location with any shipment.