The government has insisted its advice around international travel is “crystal clear”, despite criticism that the rules are confusing and ministers' comments have been contradictory.
Boris Johnson insisted the position was “very clear” saying people should only travel to an amber list country “for some extreme circumstance, such as the serious illness of a family member”.
“You should not be going to an amber list country on holiday,” the prime minister said on Wednesday.
However, his comments came on the same day environment secretary George Eustice said people could go to amber-listed countries "to visit family or indeed to visit friends" as long as they observed quarantine rules on their return.
Welsh secretary Simon Hart said “some people might think a holiday is essential” and therefore a valid reason to travel.
Earlier, health minister Lord Bethell of Romford said that all travel abroad this year would be “dangerous”.
Watch: Confusion over 'amber list' holiday destinations
Speaking at a Downing Street press conference on Wednesday evening, health secretary Matt Hancock attempted to clarify the rules, saying: “We have been absolutely crystal clear that you should not go to an amber or red list country on holiday, you should only go in exceptional circumstances.”
But Hancock added “you don’t necessarily have to ban everything” even if the government advised against it.
Asked if it was “irresponsible” to go on holiday to an amber list country, transport secretary Grant Shapps told the BBC on Thursday: “We ask people not to… that is the situation."
Shapps also defended the continued availability of direct flights from countries such as India on the coronavirus “red list”.
He told Sky News: “You cannot prevent British citizens from returning home, no country can ban its own citizens.”
On Times Radio, Shapps said an amber list country was “not free and open travel” and “we ask people not to go to these places for holidays”.
“So travel companies who stick to that and refuse to rebook, I would suggest are not in the right place.”
Ryanair boss Michael O’Leary said “most of the UK population doesn’t understand” the rules on travelling to amber-listed destinations, with people “booking in their droves” to take holidays in places not on the green list this summer.
The airline chief executive told ITV’s Peston: “People are ignoring the short-term restrictions and working out that they’ll be safe to fly in late June, July, August when the school holidays come around, and they’re booking in their literally hundreds of thousands on a daily basis.”
EasyJet chief executive Johan Lundgren described the communication in relation to amber list travel as “very confusing to say the least”.
He said customers are going on holiday to amber tier countries as many people see an overseas break as a “top priority”.
Asked if easyJet customers were flying to amber countries for leisure despite government guidance not to do so, he replied: “Yes, people are booking flights and they’re going there on holidays.
“I think that the view was to apply common sense, and I think that there’s a lot of people out there who have as a top priority coming through this pandemic to go on that holiday break.
“That is what people are doing.”
George Morgan-Grenville, founder and chief executive of travel company Red Savannah, said the industry is “facing a disaster” and cannot understand why it “has to bear the brunt of so much confused and mixed messaging from ministers”.
Further confusion came as the EU declared that it will give fully vaccinated tourists the green light to visit resorts – despite ministers insisting holidays in Spain and France remain off limits.
Portugal is currently the only major EU destination on the government’s “green list” for holidays.
The government has been under pressure over its travel policy following the introduction of the traffic light system in England on Monday, with Scotland and Wales also implementing similar approaches.
Countries on the green list can be visited without needing to quarantine on their return.
Countries on the amber list involves self-isolation for at least five days upon return to England, as well as taking two tests.
Meanwhile, those arriving from red list countries will continue to require an 11-night stay in a quarantine hotel at a cost of £1,750 for solo travellers.
Watch: How England will leave lockdown