The UK government has defended its decision to impose a 14-day quarantine on everyone arriving from Spain, after the Spanish PM called it "unjust".
"We respectfully disagree with the Spanish government's position on this," said government minister Simon Clarke.
He added that there had been a "sharp increase" in Covid-19 cases in Spain.
Spanish PM Pedro Sánchez previously said tourists in most regions would be safer from coronavirus than in the UK, and he hoped Britain would reconsider.
The UK is advising against all non-essential travel to Spain, including the Balearic and Canary Islands. It also removed Spain and its islands from the list of countries which are exempt from the 14-day quarantine rule.
On Tuesday, Germany also advised against travel to three areas of Spain.
In an interview with the Telecinco TV network, Mr Sánchez said his government was "talking with British authorities to try to get them to reconsider" the decision.
He said the UK had made an "error" by considering the infection rate for the whole country.
He added that "64.5% of the new cases registered are in two territories" and in most of Spain the prevalence of Covid-19 was "very much inferior to the numbers registered in the United Kingdom".
The rate of infection in Spain is 35.1 cases per 100,000 people, while the UK is at 14.7, according to the latest figures from the European Centre for Disease Prevention and Control.
While the outbreak remains under control in many parts of Spain, certain areas - in particular Catalonia in the north-east, which includes the city Barcelona, and the neighbouring region of Aragón - have seen a huge spike in infections.
Data up to 19 July suggested there were lower rates of infection in the Balearic and Canary Islands than in mainland Spain.
Speaking to BBC Breakfast, local government minister Mr Clarke said: "We obviously continue to work closely with them [Spain] and we wish them every success in managing this outbreak, but we've seen a very sharp increase in cases in Spain.
"A 75% increase in cases reported between the middle of last week and the end of last week. That's why we took the action that we have."
Mr Clarke responded to criticism that the government should have given more notice to travellers, saying ministers received the data on Thursday and Friday "and we acted on Saturday".
He was asked about the risk to holidays to other destinations, following a recent rise in cases in Germany and France. Mr Clarke said the possibility of the rules changing "has to be factored in".
"By all means go on holiday but understand that there is a chance you may be asked to self-isolate upon your return," he said.
On Tuesday, the UK government added Estonia, Latvia, Slovakia, Slovenia and St Vincent and the Grenadines to the list of countries which are exempt from the quarantine rule.
Travellers returning to the UK from anywhere not on the list - including Spain - must now self-isolate for 14 days at a registered address.
People who do not self-isolate can be fined up to £1,000 in England, Wales and Northern Ireland and those returning to Scotland could be fined £480, with fines up to £5,000 for persistent offenders.
Image copyright Getty Images Image caption In Barcelona, some businesses are quiet as residents are being told to stay at home Image copyright Getty Images Image caption Tourism is important for Spain's economy, with about 18 million Britons travelling there last yearFollowing a report in the Daily Telegraph that the quarantine for travellers from Spain could be cut to 10 days if they test negative, a No 10 source told the BBC they were "not expecting any move on quarantine days reduction".
Mr Clarke said "we always keep the quarantine rules under review" but "the position is totally unchanged".
Asked about the newspaper's report that 10 Britons have tested positive for the virus after returning to the UK from Spain, Mr Clarke told the Today programme: "I can't say whether it's true or not.
"What I can say is that there have been thousands of new cases in Spain over recent days, therefore it's an entirely plausible scenario that people have returned to the UK carrying the virus. Even if the risk is one that hasn't materialised, frankly it's one we need to close off."
Some travel agents say they are struggling to understand the logic of the UK government's advice.
And Labour MP Chris Bryant, who chairs the all-party parliamentary group for Spain, said: "Why the Canaries - which are further away from Barcelona than Barcelona is the UK - are on the list as well as mainland Spain, I simply don't understand.
"And there are many, many regions of Spain which have much lower infection rates than many areas in the UK. I think this has been terribly badly handled."
Labour has said the government's handling of the restrictions had been "chaotic", and has urged the government to step in to protect jobs in the travel industry.
"The airline industry and passengers need clarity," said shadow transport secretary Jim McMahon.
Holiday companies Jet2 and Tui were among those to announce sweeping flight cancellations following the UK announcement.
EasyJet, British Airways and Ryanair said they would continue to operate full schedules of flights to Spain, though EasyJet said its holidays would be cancelled for the next few weeks.
Among the thousands affected by the change in travel advice was Tom Clasby, who had checked into an airport hotel near Stansted with his fiancée, their two daughters, and other family members, ahead of a holiday to Majorca.
Mr Clasby, 26, was due to depart at 06:55 BST on Tuesday but now faces having to return home to Bury St Edmunds.
"We're in a situation where we can't do anything yet and I don't actually know what to do. The poor little girls have been so excited for this holiday - it's the second holiday this year we've had cancelled," he told the BBC.
Image copyright Tom Clasby Image caption "We are just very disappointed, the girls will be so upset," said Tom ClasbyAlso affected was Transport Secretary Grant Shapps, who flew to Spain on Saturday despite knowing a decision on the quarantine policy was due.
Mr Shapps said in a statement he would return to the UK on Wednesday in order to complete his quarantine and would return to work as soon as possible.
It comes as a further seven people with coronavirus were reported to have died across all settings in the UK, according to latest government figures - bringing the UK's total number of deaths to 45,759.
In other developments:
Campaigners have written to the health secretary to say a lack of translated coronavirus guidance is jeopardising the safety of non-English speakers in the UK A report from the Commons Home Affairs Committee says stronger action needs to be taken to protect people in asylum accommodation from the virus Emirates becomes the first airline to offer free Covid-19 insurance as it tries to get people flying againHave your travel plans been affected due to the new government advice? Have you returned to the UK and are facing problems due to quarantine? Are you still stranded in Spain? Share your experiences by emailing haveyoursay@bbc.co.uk.
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