Which? said testing providers were already struggling to meet demand, even with huge restrictions on overseas travel.
Anyone travelling to the UK must currently self-isolate for 10 days and take PCR tests on day two and eight of their quarantine. Both tests must come back negative before they can leave self-isolation after the tenth day.
However, Which? said some passengers were having to extend their quarantine, or pay for additional Covid tests, with some private labs failing to deliver test results on time.
