England’s new lockdown could be extended if the latest measures fail to halt the spread of coronavirus.
The message came less than a day after Prime Minister Boris Johnson announced a new four-week lockdown.
From Thursday, most shops will close and people will be barred from meeting relatives and friends indoors until December 2.
On Sunday, one of Mr Johnson's top ministers said the lockdown could be extended.
“It will get reviewed on December 2, but we’re always driven by what the data shows,” Cabinet Office Minister Michael Gove told Sky News.
“We will always take the decision in the national interest based on the evidence, the best information that we have.”
When pressed on whether the restrictions could be extended if the lockdown effects were not positive, Mr Gove said: “Yes.”
Mr Johnson announced the emergency measures, which allow schools, universities and courts to stay open, on Saturday after scientists said England’s health system faced being overwhelmed.
“Our hope was that, by strong local action, we could get the infection rates down,” he said.
“As we’ve seen, we have to be humble in the face of the nature and in this country the virus is spreading even faster than the worst-case scenarios.
“Now is the time to take action because there is no alternative.”
Infection rates across much of England are increasing and more people are being admitted to hospital.
Total virus cases in the UK since the outbreak began have now passed one million and the country has suffered more than 46,000 fatalities, the highest death toll in Europe.
“If we were to have a situation where we found our NHS overwhelmed, it will also have inevitable effects on our economy, on people’s overall confidence and their ability to go about their daily lives,” Mr Gove said on Sunday.
“This is a protective step that we need to take that nobody relishes. We feel that there is no alternative.”
Mr Johnson has repeatedly been urged to impose a second lockdown in recent weeks due to the infection rate doubling but has resisted the move, largely because of concerns over the economy.
The government has reversed its financial support policy, extending its furlough programme, which had been due to end on Saturday, until the end of the new lockdown.
Details of the plan were leaked after a meeting of four senior ministers.
That breach is now under investigation, Mr Gove said.