PCR tests required for most travelers average about 75 pounds ($104) each, or 300 pounds for a family of four, but many firms charge significantly more. Prices quoted by providers listed on the government website range from 17 pounds ($24) to 250 pounds ($347).

Javid said Sunday that he had asked the Competition and Markets Authority to crackdown on “unfair market practices” by test providers.

“People should be able to go on holiday, whether it’s to see family or just to relax, without fearing excessive fees for PCR tests,’’ he said on Twitter.

The watchdog has the authority to intervene directly when it uncovers unfair practices but it can also provide advice directly to ministers so they can take swifter action.

“We are aware of concerns about the evolving markets for COVID-19 tests for international travelers,” the agency said. “We look forward to providing the Secretary of State with advice on how best to ensure that travelers have access to tests that are affordable and reliable.”