The move was announced by Transport Secretary Grant Shapps on Thursday, August 20, and means people travelling from these countries will have to isolate for two weeks if they return to the UK after 4am on Saturday, August 22.
Government officials say the decision to add the three countries to the quarantine list was based on a “significant change in both the level and pace of confirmed cases”.
The weekly incidence per 100,000 people for Croatia has increased from 10.4 on August 12 to 27.4 on August 19 – a 164% increase.
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In Trinidad and Tobago, cases have increased over the past four weeks, with a sharp 232% spike in the number of cases per 100,000 people between August 12 and 19.
In Austria, the weekly number of cases per 100,000 of the population has increased from 10.5 on August 13 to 20.3 on August 20, a 93% increase.
Those who still decide to travel after Saturday will have to self-isolate for two weeks.
Mr Shapps tweeted about the change on Thursday evening and referenced his own isolation from a family holiday to Spain.
He added: “As with all air bridge countries, please be aware that things can change quickly.
“Only travel if you are content to unexpectedly 14-day quarantine if required (I speak from experience!)”
The Government also announced that Portugal was being added to the travel corridor list, meaning passengers can travel there safely from 4am on Saturday without having to quarantine on return.
Belgium, Andorra and The Bahamas were among countries removed from England’s travel corridor list earlier this month.
Scotland has also removed Switzerland from its safe travel list, so anybody returning to north of the border from there will have to self-isolate for 14 days.