The Transport Secretary Grant Shapps will have to quarantine for two weeks when he returns from Spain.
The Department for Transport confirmed that the Conservative politician is on holiday in Spain.
He will therefore be required to self-isolate for two weeks when he returns to the UK.
Mr Shapps housebound future comes after his government abruptly imposed a two-week quarantine on all travellers arriving from Spain after a surge of coronavirus cases.
The dramatic and sudden reversal on Saturday to the opening of the European continent to tourism after months of lockdown.
The quarantine requirement is due to take effect from midnight tonight, making it impossible for travellers to avoid it by rushing home.
The British foreign ministry also announced it was recommending against all but essential travel to mainland Spain, a move likely to prompt tour operators to cancel package holidays and trigger claims against insurers.
Spain’s Canary and Balearic Islands were not covered by the advice to avoid travel to the mainland, but holidaymakers returning to Britain from the islands will still be subject to quarantine on return.
Britain’s government urged employers to be “understanding” towards staff who are unable to return to their place of work for two weeks after they return from holiday.
The sudden British move followed steps this week by other European countries.
On Friday Norway said it would re-impose a 10-day quarantine requirement for people arriving from Spain from Saturday, while France advised people not to travel to Spain’s northeastern region of Catalonia.
But the total collapse of tourism from Britain would have far more impact. Britain accounted for more than 20% of the foreign visitors to Spain last year, the largest group by nationality.
Tourism normally accounts for some 12% of Spain’s economy.
Spain had been on a list of countries that the British government had said were safe for travellers to visit – meaning tourists returning home would not have to go into quarantine.
The announcement of such lists just weeks ago had allowed Europe’s tourism sector to begin its revival after the near total shut-down prompted by the COVID-19 pandemic.
Responding to the British measures, Spain said on Saturday it was a safe country with localised, isolated and controlled outbreaks of the oronavirus.
A Spanish Foreign Ministry spokeswoman said Spain “respects decisions of the United Kingdom” and was in touch with the authorities there.
The British move will affect not just Spain’s tourism sector but airlines and travel companies struggling to get back to business.
Britain’s opposition Labour Party said the news was “deeply concerning” and called for support for British people affected.