Senior Tories have condemned the Government for their "unfair" lack of clarity over the possible implementation of further quarantine restrictions.
Chairman of the 1922 Committee of backbench Tory MPs Sir Graham Brady and former Conservative Party leader Sir Iain Duncan Smith have called for a "proper testing regime for air travellers" to be implemented as quickly as possible, and for regional air corridors to be considered.
It comes as Chancellor Rishi Sunak warned holidaymakers of the risk of travelling abroad during the coronavirus crisis amid concerns France may be the next nation to be added to the quarantine list.
He said on Friday that ministers will "not hesitate" in ordering travellers coming back from countries with high Covid-19 rates to isolate for 14 days, as Belgium, Andorra and The Bahamas lose their exempted status.
Travellers returning to the UK from those three nations from Saturday must enter quarantine, and there are fears those coming back from France could be next with cases there increasing.
Sir Graham told The Telegraph leaving the public in the dark on the matter is "grossly unfair".
"We should move to a proper testing regime for air travellers as quickly as possible, but in the meantime it is essential that the Government is as transparent as possible about the criteria which are being used judging which countries require quarantine and which do not.
"Leaving the travelling public in the dark is grossly unfair and is causing further damage to the holiday and leisure sector," he said.
Sir Iain added that holidaymakers needed more information and for it to be clearer so they could make better informed decisions about whether to travel abroad.
He also called on the Government to reconsider regional travel corridors and testing to replace the "blunt" approach of quarantine.
"People are travelling to countries at the moment and they have no idea whether they will or will not have quarantine reimposed," he told the paper.
"My only question is can the Government not look at regional quarantine so that people could travel to low-risk areas like Majorca but not Barcelona?"
The comments come as Eurostar said it recorded an increase in passengers travelling on its trains from Brussels to London on Friday, beating the deadline.
Mr Sunak told Sky News: "It's a tricky situation. What I can say to people is we're in the midst of a global pandemic and that means there is always the risk of disruption to travel plans and people need to bear that in mind.
"It's the right thing for us to do to keep everything under review on a constant basis talking with our scientists, our medical advisers, and if we need to take action as you've seen overnight we will of course not hesitate to do that and we're doing that to protect people's health."
France's coronavirus rate has increased steadily in the past month to 13.2 new infections per 100,000 people, suggesting the spread is worse than in the UK, which has a rate of 8.4.
However, France still appears to be faring better than Belgium, which has seen its rate soar to 27.8. It also has a rate lower than Spain's when it was added to the restriction list at around 27.4.
On Thursday, Transport Secretary Grant Shapps said rising Covid-19 infection levels in Belgium, Andorra and The Bahamas meant they would be added to the quarantine list.
The measures come into force in England, Scotland and Northern Ireland from 4am on Saturday after they were introduced in Wales from Friday.
The Foreign and Commonwealth Office also updated its travel advice to warn against all but essential trips to the three countries.
The Department for Transport clarified that people driving to the UK from Germany or the Netherlands via Belgium will need to self-isolate for 14 days unless, while in Belgium, all passengers remain in their car and no-one joins them.
Anyone who travels on a train which passengers get on or off in Belgium will also need to quarantine.
This means Eurostar passengers travelling from Amsterdam to London will need to self-isolate, as the journey involves changing trains in Brussels.
Elsewhere, Brunei and Malaysia have been added to the Government's travel corridor list, following a decrease in confirmed cases of coronavirus, meaning arrivals from these countries no longer need to quarantine.
In Andorra, new cases per week have increased five-fold since mid-July, while in The Bahamas the weekly case rate peaked at 78.6 last week, up from 3.1 in the middle of last month.