The measure will take effect in England from 4am on Monday 19 July. This is the same time the rules change on quarantine for people arriving from amber destinations. From Monday, people who have received both Covid vaccinations, and under-18s, will not have to isolate after returning from countries on the amber list.

However, they will still have to take a test three days before returning and have a PCR test on day two back in the UK. Currently, arrivals in England from amber countries have to self-isolate for 10 days on their return.

Moving the Balearic Islands from the safe green travel list – which doesn’t require quarantine on return – to the amber list is likely to mainly impact younger adults, as they are more likely to have not received both coronavirus vaccinations. They are also the age group which typically goes on holiday to Ibiza, Majorca and Minorca.

Rory Boland, Which? Travel editor, said: “These changes further highlight that anybody considering booking a holiday this summer should only do so if they are prepared to rebook, often at extra cost, and potentially face more expensive testing or quarantine if the rules suddenly change.

“It can be near impossible to get your money back in these circumstances, and while flexible booking policies that offer to rebook your holiday for free can be of use, the devil is in the detail. You will always have to pay any difference for new dates, and price increases can be significant.”

Transport secretary Grant Shapps said that since the Balearics were moved to the green watchlist two weeks ago “we’ve seen the rates double and also the rate of positivity of these tests double, meaning that we’re going to need to move quickly, as we said we might always have to do”.

But the latest figures show the infection rate for the Balearics is 205 cases per 100,000 people, compared with 329.9 for the UK. So, you’re more likely to catch Covid-19 in the UK than on the Spanish islands.

The British Virgin Islands are also being moved to the amber list from Monday. Bulgaria and Hong Kong are moving to the green list, meaning people arriving in England from these countries don’t need to quarantine.

Croatia and Taiwan are being moved to the green watchlist, meaning there is a possibility they will be moved to the amber list at some point. Cuba, Indonesia, Myanmar and Sierra Leone will be added to the red list.

People returning to the UK from green list countries can do so without the need to isolate. However, travellers whether vaccinated or not, will still need to pay for Covid tests when returning from destinations on either the green or amber list. Arrivals from red list countries must pay to self-isolate in a hotel for 10 days.