The prime minister has warned people against travelling to amber list countries on holiday or for leisure purposes, amid mixed messages from ministers on international travel.
"I think it’s very important for people to grasp what an amber list country is: it is not somewhere where you should be going on holiday, let me be very clear about that," Boris Johnson said.
Thousands of people have reportedly travelled to destinations on the amber list since the ban on foreign holidays was lifted, such as France, Greece, Spain and the US. More than 150 flights are reported to have left on Monday.
The PM – who says he remains hopeful about ending all of the UK’s lockdown measures in June despite concern over the so-called Indian variant – stressed that if people do go to a country on the amber list, they "absolutely" have to do so "for some pressing family or urgent business reason".
"Please bear in mind that you will have to self-isolate, you’ll have to take tests and do your passenger locator form and all the rest of it," he said.
International leisure travel resumed in England on Monday as part of the government’s roadmap for easing COVID-19 restrictions.
A traffic light system is now in place, with nations given a green, amber or red list designation based on their coronavirus situation.
Countries on the green list – such as Portugal and Israel – can be visited without the need to quarantine upon arrival back in the UK. People still need to complete pre and post-departure COVID tests.
People returning from amber list destinations have to quarantine at home after coming back, as well as taking a series of COVID tests and completing a passenger locator form.
UK citizens returning from red list countries have to quarantine at a government-approved hotel for 10 days, at a cost of £1,750 for a solo traveller.
Nations on the red list include India, Turkey and Brazil.
But Yvette Cooper, a senior Labour MP and chairwoman of the Home Affairs Select Committee, has expressed fears that queues and delays at airports could result in "super spreading" if extra safety measures are not put in place.
Sky News has obtained footage from Heathrow Airport on Sunday evening, which shows passengers from red list countries queueing for passport control alongside people returning from other destinations.
Sunny Kapoor was returning from a funeral in India and filmed what he described as a "chaotic" scene.
"I was just amazed that as soon as you came off the aircraft, without any social distancing at all, it was quite shocking for me," he said.
Meanwhile, a health minister risked sowing confusion when he indicated in the House of Lords that people should not be going abroad full stop.
"Travelling is dangerous. That is not news to us or to the people who get on those planes in the first place," Lord Bethell said.
"We do ask people, particularly as we go into the summer, travelling is not for this year, please stay in this country."
Welsh Secretary Simon Hart told Times Radio that people should use their "common sense" when it comes to travelling to amber list countries.
He said people should only go to amber list countries "if it is essential" and that "some people might think a holiday is essential".
The PM’s line on travel to amber list countries was echoed by his spokesman, who was speaking at a regular briefing for journalists.
"The position remains that people should not travel to amber list countries and that is to protect public health," he said.
"There are some limited reasons why it might be acceptable to travel – for work purposes, protecting essential services or compassionate reasons such as a funeral or care of a family member – but otherwise people should not be travelling to these countries."
When asked why the government dropped £5,000 fines for people found to be going on holiday to amber list countries on Monday, the spokesman said the country was moving to a different stage of the epidemic, one in which people should take personal responsibility for their actions.
"We are working with the travel industry and others on this. All of us have a personal responsibility to protect one another as we cautiously reopen international travel," the spokesman said.
"That is why it is important when proceeding to go on something like a holiday people stick to the green list.
"We are moving to a situation where the public can take responsibility for their actions. I think it is important to stress that by and large that is what we are seeing.
"Obviously we will keep this under review, we are keeping a careful eye on this and we will take further action if necessary."
It comes after a minister suggested people could travel to amber list countries to visit family and friends.
"We don’t want to stop travel altogether and the reason, as [Health Secretary] Matt Hancock set out, that we have the amber list is there will be reasons why people feel they need to travel either to visit family or indeed to visit friends," Environment Secretary George Eustice told BBC Radio 4’s Today programme.
"They can travel to those countries but they then have to observe quarantine when they return and have two tests after returning.
"So people can travel to those areas, yes, but they will then have to subject themselves to the quarantine requirements on return."
Labour’s shadow home secretary Nick Thomas-Symonds said the government’s border policy had "unravelled into dangerous chaos" within hours of travel resuming.
"There is a lack of strategy, which has meant the UK government, and their own ministers, are giving out conflicting and confused advice about whether people are allowed to travel, especially between amber list countries," he said.