The CMA said it had “raised concerns” with Randox, which is one of the UK’s largest test suppliers, about some of its terms and conditions, as part of the regulator’s wider investigation into Covid-19 testing sector.

Following these talks, Randox has made several changes to its terms and conditions, including the promise to give clearer information to customers on when it will provide PCR tests and results.

Randox will also improve notification of customers’ legal rights on cancellations and refunds, and remove terms suggesting customers are not entitled to compensation if things go wrong.

CMA chief executive Andrea Coscelli said: “With recent changes to the rules for travel, the spotlight is once again on PCR testing providers and their practices.

“I am pleased that Randox has agreed to change its terms, which means consumers benefit from their legal rights to cancel and get a refund, and are not stopped from pursuing compensation if there is a problem."

Coscelli added that it was “essential that all companies play by the rules and treat people fairly”.

“We are clear that, if they fail to do so, they risk facing enforcement action from the CMA or trading standards,” he said.

“We recently provided recommendations to government on changes to better protect consumers in this market and we hope that, given the reintroduction of PCR testing for travellers, these will be implemented as quickly as possible.”