Speaking during the Scottish government’s daily coronavirus briefing on Tuesday (28 July), Sturgeon said holidaymakers should not assume the rules in-destination at time of booking, or during their trip, will be the same once they come to take their holiday, or head home.

She said Europe was experiencing a "worrying resurgence" in Covid cases, noting spikes in Belgium, Germany, France, and most notably Spain.

The Department for Transport on Saturday (25 July) revoked Spain’s travel corridor, effectively re-imposing a two-week quarantine requirement on arrivals into England from Spain – including returning holidaymakers. The other three home nations took the same precaution simultaneously.

The Foreign Office has also since updated its travel advice to advise against all non-essential travel both to mainland Spain and its islands, in spite of their lower rates of coronavirus infection.

"As the prevalence of Covid in Scotland continues to fall, we must guard against the risk of cases coming into the country from outside," said Sturgeon.

"If necessary, the Scottish government will reimpose quarantine restrictions on travel from certain countries, as we did at the weekend for Spain, if those countries see a sharp increase in cases.

"People planning overseas holidays need to be aware of that. You cannot assume the rules and regulations applying to, or in, your destination when you book a holiday will stay the same while you are there, or be the same when you come to travel home.

"My advice to you remains to be very cautious about non-essential foreign travel at this time. If you are in a position to have a holiday, and want to take a holiday, the safest way of doing so is to stay here in Scotland so you avoid the risks of foreign travel but you are also, as an added bonus, helping the Scottish tourist industry as well."

Sturgeon said the situation in Spain could be repeated in Scotland if the country "drops its guard". "For the government, that means we must continue to guard against a surge in cases, and sometimes that will involve us taking unpopular and difficult decisions – but we will not shy away from that if that is necessary to help protect the country.

"Last week, we were talking about Spain, which at that point we had decided to put on the exempt list for quarantine. I made the point then – these things are not set in stone."

The first minister said the unpredictable nature of the virus meant the situation was prone to changing quickly from a position "where it looks as under control to rising again very quickly", pointing towards Spain as an example.

"Last week, because the most up-to-date data we had on Spain showed its [virus] prevalence was closer to Scotland, we thought – given the impact on of these decisions on the aviation and tourist sectors – that we could make a move on Spain," said Sturgeon.

"But the data we then saw at the weekend showed there had been a doubling of cases in the most recent weeks. That’s unfortunately the basis on which we have to take these decisions.

"All of that leads me to advise [being] very cautious about non-essential foreign travel right now because it is very unpredictable. I know that’s really frustrating for people who want to go on holiday after a very difficult few months, but you cannot be certain that situation won’t change while you are away.

"I wouldn’t, if you’re asking me, be booking a foreign holiday right now because of these reasons. If I had the time to go on holiday, I’d be choosing to spend it here in Scotland."