Health Secretary Matt Hancock has admitted he is “concerned” after the daily number of UK coronavirus cases reached its highest level since May.
Official figures show 2,988 new COVID-19 infections were reported in a 24-hour period.
It is a large rise on Saturday’s figure of 1,813 infections.
Sunday’s number is the highest daily total since 23 May, when there were 2,959 cases.
Mr Hancock said there had been rises across Europe, and that it was “so important that we do all we can to prevent that happening here”.
He added that the new positive tests were predominantly among younger people, but warned that this could lead to a rise across the population as a whole, because it had happened elsewhere.
He said: “It’s so important that people don’t allow this illness to infect grandparents and lead to the sort of problems we saw earlier in the year.”
Mr Hancock said that while more people were being tested, “the proportion that tests positive is going up as well”.
He said it was important that everyone “does their bit” by observing social distancing, and insisted that schools and workplaces are “Covid-secure”.
Asked about another lockdown, he replied: “We’ll take whatever action is necessary.”
Scotland’s First Minister Nicola Sturgeon said the daily rise “reminds us again of the need to be very vigilant”.
Labour’s shadow health secretary, Jonathan Ashworth, tweeted: “Deeply concerning increase in cases and a stark reminder there is no room for complacency in suppressing Covid.”
He added that Mr Hancock “must come to (the) Commons tomorrow” to explain the latest government position on testing.
Overall, 347,152 cases have now been confirmed.
Two more coronavirus-related deaths have also been reported in the UK. It takes the total to 41,551.
Separate figures from statistics agencies show there have now been 57,300 deaths registered in the UK where COVID-19 was mentioned on the death certificate.
The rules apply to meetings indoors and outdoors, unless a person is part of a support bubble, Bolton Council said.
Bolton is the worst-affected area in the country, with a weekly infection rate of 99 cases per 100,000 people, overtaking Pendle (71.1), Oldham (55.6) and Blackburn with Darwen (48.3).
Comparisons between recent and past cases should be made with caution.
The number of confirmed cases is heavily dependent on how many people – and who – is tested.
This has changed significantly since the start of the pandemic, with the number of tests processed each day increasing significantly.
Community testing has also expanded, whereas previously, access was limited to symptomatic patients and key-workers.
The R number is a measure of how many people, on average, each infected person transmits the virus to.
The latest government data shows how the number varies across different parts of the UK.
While England has an estimated R number of between 0.9 and 1.0, Wales has an estimated number of between 0.5 and 0.9.
Scotland’s R number is estimated to be between 0.9 and 1.4.
The number could be as high as 1.6 in Northern Ireland.
Analysis: Social distancing as important as it has ever been
By Laura Bundock, news correspondent
It is perhaps not a surprise that the number of people testing positive has gone up.
It could well be driven by results from areas with local outbreaks, where there is increased testing.
And if you have a virus hotspot, and you test more people there, you will naturally pick up more cases.
What we aren’t seeing is a rise in the number of people in hospital, which is good news.
But, of course, no one wants more cases of COVID-19, because the worry is they start to seep into the older population who are more likely to be seriously ill.
So, the figures are another reminder that the virus hasn’t gone away – that hand hygiene and social distancing are as important now as they ever have been.