The green list currently only includes 11 countries and territories after Portugal was removed last week due to rising Covid-19 cases.

The travel industry’s hopes that more countries could be added to the green list during the next review, due by 28 June, could be dashed by the government’s “very cautious” approach, according to The Guardian.

Government sources are quoted as saying any changes to the green list would be based “purely on public health considerations”, amid fears about fast-rising cases of the Delta variant, which was first identified in India, and exceeded 11,000 new infections in the UK on Thursday (18 June).

“My sense is that we’ll continue to be very cautious in thinking about how we take any steps that could increase transmission,” a government source said.

While another Whitehall insider said the government was keen to avoid taking any measures that could jeopardise the new date for the ending of all restrictions in England on 19 July.

The government has admitted it is considering allowing fully vaccinated people returning from amber countries to be exempt from the current 10-day quarantine requirement. Although this proposal is believed to be in its “early stages”.