Denmark has been removed from the Government's list of travel corridors due to widespread outbreaks of Covid-19 in its mink farms, the Transport Secretary said.
Travellers arriving in the UK from the country after 4am on Friday must self-isolate for 14 days.
Grant Shapps said in a statement: "I understand that this will be concerning for both people currently in Denmark and the wider UK public, which is why we have moved quickly to protect our country and prevent the spread of the virus to the UK.
"While new lockdown rules mean leaving home in order to travel for holidays is no longer permitted, the government's travel corridor policy remains a critical part of the Government's Covid-19 response as it mitigates the risk of importing infections from abroad."
Denmark was only added to the quarantine-free list on October 25.
The move comes just hours after Germany and Sweden were removed from the list, with people travelling to the UK from those destinations to quarantine for two weeks if they arrive after 4am on Saturday.
Germany's seven-day rate of coronavirus cases per 100,000 people reached 140 after nearly 20,000 cases were reported on Wednesday.
The rate for Sweden is 190.
Figures have been calculated by the PA news agency based on data collected by the European Centre for Disease Prevention and Control.
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The Government is believed to be using a rate of 100 as the threshold above which it considers triggering quarantine conditions. This is up from 20 in recent months.
The UK's own rate is 235.
Mr Shapps has launched a taskforce to develop methods of reducing the 14-day self-isolation period for people arriving from non-exempt locations.
He said the Government was considering a "test and release regime" which would still involve a quarantine period of at least a week.
