Travellers from these destinations will not have to quarantine on arriving in the UK regardless of whether or not they are fully vaccinated. However, they will still need to take pre-departure and day two tests and complete a passenger locator form.

Thailand and Montenegro will be added to the red list from 30 August 2021, reflecting the increased case rates in these countries and the higher risk that travel from these countries poses to UK public health.

The government says that high coronavirus rates combined with lower levels of published genomic surveillance in Thailand and Montenegro than other countries mean that an outbreak of a new variant or existing variants of concern or variants under investigation cannot be easily identified before it is imported and seeded across the UK.

Passengers arriving in the UK from these red list destinations will need to isolate for 10 days in a managed quarantine facility and follow the necessary testing requirements.

The government says all classification changes have been decided by ministers, informed by the latest data and analysis by the Joint Biosecurity Centre (JBC) and wider public health considerations, to help the public understand the risks to UK public health from incoming travel from different destinations.

Rory Boland, Which? Travel editor, said: “As the green list grows, so do the numbers of people travelling. With several European destinations added, more people will be looking to head abroad. However, unless the government and regulator moves swiftly to fix the issues surrounding the overstretched and unreliable private testing system, many more travellers could have their travel plans ruined and be left out of pocket.

“Travelling abroad this summer carries considerable risk. Consumers that do decide to book should make sure they go through reliable holiday providers with good, flexible booking policies. Which? Travel’s Holiday Checker tool has ranked more than 70 holiday providers to compare their booking flexibility and cancellation policies.”

Earlier this week the Competition and Markets Authority (CMA) warned PCR test providers against breaking consumer law. Some providers have misled consumers over prices, failed to deliver tests or results in stated timescales, or refused refunds where an advertised service isn’t delivered.