A group of friends who were on holiday in Portugal when it was reclassified said they were made to feel like criminals.
Cheslyn Baker claims she was placed in 'prison' like isolation when she returned from the western European country.
The Swannington, Leicestershire woman had jetted out to Portugal with some pals after the nation was classified as green in May, Leicester Mercury reported.
Under the government's traffic light system, that means no self-isolation or quarantine is required upon return to the UK.
Cheslyn, whose friend has a holiday home in Portugal, said: “At last we could go out with a friend back to her home in the southern Algarve, after many months of lockdown.”
They booked Ryanair flights from East Midlands Airport on June 3, having taken a compulsory Covid test costing £160 each.
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As they filed towards the boarding gate they heard a rumour that the UK was considering taking Portugal off the green list.
Cheslyn said: “We thought it wouldn’t happen as cases there - especially in the Algarve - were so low, otherwise we wouldn’t have considered going in the first place.”
The three friends, who are all fully-vaccinated, had been in the Algarve for a couple of days when they had confirmation that Portugal was destined for the amber list.
British tourists and Portuguese people were at first bemused, then angry, Cheslyn said.
As well as being 'locked up' in her Leicestershire home for 10 days after she returned, she was made to pay a 'fine' because the three extra PCR tests came to about £300.
“To me it felt like we, as British citizens, had committed a crime," she said.
"We were certainly receiving a hefty fine in costs of three further PCR tests and a prison sentence of 10 days in the form of self-isolation, plus daily check ups at random, not to mention visits by officials to make sure we were staying put.”
All travellers back to UK were also newly required to produce proof of orders and payments for tests yet to be taken on days two and eight of their isolation.
They also had to show a negative Covid test certificate at the airport and fill in another long Passenger Locator Form.
However, it wasn’t until they reached the boarding gate at Faro to fly home to East Midlands Airport that they were asked for these documents, the friends claim.
Two passengers who were meant to be on their flight weren’t allowed to board the plane home as their results were on email, which they couldn't access because of poor mobile reception.
Cheslyn said: “Some of the measures, haphazard and unclear as they were, are understandable to prevent the spread of Covid. Other rules aren’t at all clear or understandable.
“Having to take so many costly negative PCR tests, then also to be put into 10 days’ isolation and ordered not to go outside anywhere at all during that time, even to walk the dog, seems illogical.
“It all seems too draconian and far too punishing to UK citizens who have already more than proved, at great cost to themselves, that they are Covid free.
“The government should at least clarify in plain language the scientific reasons for prohibitive measures they take with travel.”
In comments at the time of Portugal's switch from green to amber the Department for Transport said the situation in Portugal "required swift action to protect the gains made with the vaccine rollout".
