The UK “will not hesitate” to add more countries to its travel quarantine list in order to protect public health, the chancellor has said.
Rishi Sunak told Sky News “there is always the risk of disruption” to holidays during the coronavirus pandemic.
It comes amid a surge in cases in France.
Belgium has one of the highest coronavirus case rates in Europe at 49.2 per 100,000 people, compared with 14.3 per 100,000 in the UK.
According to the European Centre for Disease Prevention and Control (ECDC), France recorded 23.4 cases per 100,000 people in the last two weeks.
It has recorded its highest number of daily coronavirus infections in more than two months, with figures on Wednesday showing 1,695 new cases reported within 24 hours.
Asked whether tourist destinations such as France could be next to be added to the quarantine list, Mr Sunak said it was “a tricky situation” and that holidaymakers needed to bear the risk of potential disruption to their travel plans in mind.
He said No 10 was doing “the right thing”, keeping the situation “under review on a constant basis” and consulting with scientists and medical advisers. If action was needed, the government would “not hesitate to do that”, he said, in order “to protect people’s health”.
The new rules for Belgium, the Bahamas and Andorra have already come into force in Wales and will take effect in the rest of the UK from 04:00 BST on Saturday.
Quarantines have already been re-imposed for travellers from Spain and Luxembourg.
But people arriving England and Wales from Brunei and Malaysia will no longer need to self-isolate, after a decrease in confirmed coronavirus cases there.
People who do not self-isolate when required can be fined up to £1,000 in England, Wales, and Northern Ireland and those returning to Scotland could be fined £480, with fines up to £5,000 for persistent offenders.