Britain on Wednesday urged private Covid test firms to stop exploiting travelers after a former competitions chief said the market was a "rip-off jungle".
"We've been clear it is unacceptable for any private testing company to take advantage of holidaymakers," the Department of Health and Social Care said in a statement.
"The government has taken action to drive down the cost of tests for international travel."
The call came one day after Britain rolled out new travel curbs to try and prevent transmission of the Omicron variant.
The price of private Covid testing has fallen considerably this year in the face of pressure from the government and the travel industry.
However, Lord Andrew Tyrie, former chairman of the Competition and Markets Authority, labeled the market a "rip-off jungle".
Tyrie told the BBC on Wednesday that "misleading online advertisements, overpricing (and) unacceptably poor service... are still widespread" in the market.
"To allow this to continue over the peak Christmas period would be scandalous," he warned.
Under this week's new rules, anyone traveling to the UK will have to show evidence of a negative lateral flow or PCR test taken within 48 hours before boarding a flight.
This will apply to travelers aged 12 and over from any country.
Travelers already have to take a PCR test within two days of arrival in Britain.
The UK travel sector argues that the cost of British tests remains a major disincentive.
The Association of British Travel Agents on Tuesday warned that the latest curbs risked holiday firms going bust.
The ABTA industry body also urged the government to provide financial support to the beleaguered sector.