Transport Secretary Grant Shapps has arrived back in the UK after cutting short his Spanish holiday to deal with the quarantine chaos.
Mr Shapps will have to self-isolate at home for 14 days after falling foul of the Government's sudden decision to axe quarantine-free travel with Spain.
The senior Tory had already flown out to Spain for a summer break with his family on Saturday when ministers decided to scrap the so-called travel corridor with the country.
The move, which came following a spike in cases in the country, has caused chaos for airlines and the travel industry at the peak of the summer holiday season.
And Brits already in Spain were left at the mercy of their employers over whether they will be supported while they quarantine back in the UK.
Mr Shaps told reporters that he "cannot rule out" other countries being added to the UK's quarantine list and insisted the measures were the "right thing to do".
He said: "We absolutely have to act the moment we get the information and that's exactly what happened with Spain as we saw and as we've seen over the weekend where there was over 6,100 cases - the highest since the peak in March over there.
"It was the right thing to do and it's why the whole of the UK did (it) at the same time.
"I can't therefore rule out other countries having to go into the quarantine as well."
Ministers did consider exempting the Balearic Islands and the Canary Islands, where the cases are lower than mainland Spain, Mr Shapps said.
But he said the chief medical officer Chris Whitty was "concerned" by soaring infection rates and wanted to see what was happening in the islands.
Mr Shapps said he understood the frustrations of tourists caught out by the rule changes, saying he was "very, very sorry and upset" for those affected - as well as those unable to go away due to the uncertainty.
He went on: "But it's absolutely essential we acted when we did, it's why all four nations of the United Kingdom acted together and the figures since have turned out to justify that action.
"We have to, I think, have a clear message and make sure that we act by adding entire countries to that list for the time being."
As ministers came under pressure over their chaotic handling of the quarantine policy, Mr Shapps abandoned his holiday to return to the UK to deal with the crisis.
In a statement at earlier this week, Mr Shapps said he had been in "constant contact" with officials and industry representatives since he arrived in Spain but he needed to "get back to work in the UK".
He added: "The sooner I get back from Spain myself, the sooner I can get through quarantine."
