Video report by ITV News Political Correspondent Daniel Hewitt
The government has stood by its decision, after the UK's most popular holiday destination saw a spike in the number of coronavirus cases.
But holidaymakers have spoken of their anger and frustration at having to follow strict quarantine rules upon their return at such short notice.
ITV News Political Correspondent Paul Brand has more:
The future of Brits' holidays to other destinations now looks uncertain, with the "chaotic nature of the decision making" under criticism and fears of a second wave of Covid-19.
Health Minister Helen Whately said Spain had seen a "very rapid increase in rates" of coronavirus and warned the list of safe countries is being kept "under review".
She said if other countries see rates "going up significantly and rapidly, we’ll need to take action".
Labour's Nick Thomas-Symonds criticised the government's actions over the weekend, describing it as "chaotic".
"Yes, of course, you have to put protective measures in place when you have a spike in cases in other countries," the shadow home secretary said.
But added: "When you do it - make sure you give people the support alongside it that they need".
Mr Thomas-Symonds said the public should not be "left with dilemmas" about what to do if they have been impacted by "swift decisions" made by the government.
Shadow Home Secretary, Nick Thomas-Symonds, criticises government's "chaotic" decision making:
He told ITV News: "We don't want people to be left with dilemmas between doing the right thing for public health and their own financial well-being, on the other."
The decision to remove Spain from the list of safe countries was announced on Saturday night, less than five hours before it came into force.
Close to 1.8 million holidays are likely to have been thrown into chaos by the move, according to travel company The PC Agency.
There are now fears more European holidays could be thrown into disarray, with fears other countries could be struck off the 'air-bridges' list at potentially short notice.
The Telegraph reported that officials in both France and Germany have warned of possible new lockdowns as parts of Europe brace for a second wave of Covid-19 infections.
Holidaymakers arriving back from Spain react to the fact they now must stay in quarantine for two weeks
French health authorities said at the weekend that the country’s R-rate was up to 1.3 and that daily new infections on Friday had risen to 1,130 - both indicators resembling those seen in May, when France was coming out of its strict two-month lockdown.
It raises the possibility people will be put off booking anything now that they know they could be made to quarantine with just hours' notice.
Travel companies have also criticised the government over the announcement.
Andrew Flintham, managing director of TUI UK and Ireland, described the current advice as "a little bit, interesting, shall we say."
He told ITV News: "One of the things as an industry we're asking for, and certainly at TUI we're asking for, is that we make it simple for customers.
"Because you've got this confusing picture where the travel advice says you can go but you have to quarantine.
"That's quite a confusing picture to try and explain to somebody.
Mr Flintham said the company was calling for a "regionalised structure" to quarantine advice, based on levels of infections in different areas rather than the country as a whole.
He added: "We don't want to take anyone anywhere where potentially they're going to be unsafe, that's the last thing we want to do. But we think there may be some ways of navigating how this virus moves around."
Airline Jet2 has called for "clarity and consistency from the government." In a statement, the company added: "We understand that this is a fast-moving situation, however the information we are receiving is contradictory and often comes with little or no notice."
ABTA, the UK's trade association for tour operators and travel agents, has echoed calls for a more "targeted approach" in the government's travel advice.
Sean Tipton, a spokesperson for the group, told ITV News: "We're fully supportive of the government and its efforts to control coronavirus outbreaks.
"But it's a question of, if you have an issue in a particular part of a country, we do feel maybe have a look at more targeted approaches.
"Particularly when you have a country like Spain with all those geographical issues. Mainland Spain, it's a big country for starters. But also it has its islands. They, by their very nature, they may be Spanish - but they're not part of Spain geographically."
The government has said that so-called air bridges to other countries are constantly “under review”.
Health minister Helen Whately told BBC Radio 4’s Today programme: “What we said throughout the time when we’ve put in place the policy on the travel corridors, the air bridges, is that we would need to keep those under review, that we would need to monitor the rates in other countries.
“That is exactly what we’ve done in Spain, so we are enacting the policy that we committed to doing.
“The rate was going up very rapidly in Spain and we had to take very rapid, decisive action.”
Speaking on Sunday, in the wake of the announcement on Spain, Foreign Secretary Dominic Raab said the government “can’t make apologies” for the decision and refused to rule out rescinding further so-called travel corridors.