After days of leaks and briefings from government on international travel rules, holidaymakers have been told to wait until Thursday for any clarity.
She advised prospective travellers: “Maybe they better wait till the government actually announces what it’s going to do as opposed to the speculation.
“That’s something I would definitely advise.”
On 16 July travellers to France, the second-most popular destination for British holidaymakers after Spain, were told that they must quarantine on return – even if they have been fully vaccinated.
The foreign secretary, Dominic Raab, later explained that concerns about the Beta variant on the French island of Réunion had led to the effective travel ban.
Twenty-four hours later, a different minister told the same programme that a new “amber watchlist” category would help holidaymakers in their decisions.
But on Monday night plans for the “next stop red list” category were scrapped.
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Ms Keegan said: “I know there’s been a lot of speculation in the press about what the system is going to be and obviously we’ve explored many options.
“But effectively what we want to do is keep it simple enough for people to really understand and obviously be able to take their own decisions based on the system.”
Paul Charles, chief executive of the travel consultancy The PC Agency, said: “The simplest and most logical system the government could introduce is the American approach, enabling fully-jabbed citizens to travel to most countries without restrictions or excessive testing on return.
“We need an easy-to-understand, consistent system, not one changed on a whim on a Friday night. Ministers have an opportunity to provide clarity this Thursday, as well as widen the green list substantially.”
Jim McMahon, the shadow transport secretary, has called on ministers to publish the data behind the decisions.
“Time and time again they’ve refused to be straight with the public and industry,” he said.
The Office for National Statistics has written to the Joint Biosecurity Centre to urge greater transparency in the reasons for placing France in the new category.
Watch: COVID-19: No prospect of amber watchlist this week - as next travel update confirmed for Thursday