Canada has led a number of destinations added to the green list for arrivals into the UK.
Also included are Denmark, Finland, Liechtenstein, Lithuania, Switzerland and the Azores, with the changes coming into effect from 04:00 on Monday.
The government said the risk travel from these countries poses to public health is “low”.
Travellers from these destinations will not have to quarantine regardless of whether they are fully vaccinated, but will still need to take pre-departure and day two tests and complete a passenger locator form.
Thailand and Montenegro will, however, be added to the red list.
This reflects increased case rates in these countries and the higher risk that travel therefore poses to UK public health.
The high rates combined with lower levels of published genomic surveillance in Thailand and Montenegro mean that an outbreak of a new variant of Covid-19 cannot be easily identified before it is imported and seeded across the UK, the government said.
Passengers arriving in the UK from these red list destinations will need to isolate for ten days in a managed quarantine facility and follow the necessary testing requirements.
Responding to the news, Mark Tanzer, chief executive of ABTA, said: “The latest travel update provides some stability to international travel as well as reassurance for holidaymakers heading off to popular holiday destinations over the coming weeks.
“The government now needs to focus its attention on sorting out some of the structural issues that are stopping people travelling and delaying the recovery.
“The UK may be leading the way on the vaccine rollout, but it is lagging behind other countries when it comes to opening up international travel and making it easy for people to travel.”
He added: “The government can and should do more to capitalise on the successful vaccine roll out in the UK – our neighbours across the channel have been able to travel without restriction for quite some time if they have been double vaccinated.
“The expensive testing regime is putting people off taking a holiday overseas and is unnecessarily onerous when people are returning from low-risk countries.”
Charlie Cornish, chief executive of Manchester Airports Group was slightly more enthusiastic.
He said: “This announcement will have a positive impact on the options available to those looking to go on holiday in the remaining days of the summer season.
“But in reality, these changes will make little difference to the overall recovery of the UK travel industry, which is already recovering at less than half the pace of the rest of Europe.
“Europe’s stronger recovery has been driven by the removal of testing requirements on vaccinated travellers.
“Unless the UK also removes the need for people with full immunity to take these tests, we will continue to squander the advantage our world-leading vaccination programme was supposed to deliver, while passengers on the continent travel restriction-free to low-risk destinations.
“Government cannot wait until the October 1st to make changes to the travel regime and must press ahead with an overhaul of its traffic light system immediately.
“We must arrive at a simpler, more affordable and sustainable travel framework to enable the best possible winter season and give customers the confidence to book ahead for 2022.”