The UK is entering a "period of particular concern" as the number of coronavirus cases rise across the country, the housing secretary says.
Robert Jenrick said "we all have to be very cautious" after 2,948 new UK cases were recorded on Monday.
It comes after two of the government's scientific advisers gave stark warnings over the rise in cases.
England's deputy chief medical officer, Prof Jonathan Van Tam, said the increase was of "great concern".
Virus cases were "increasing exponentially", according to another member of the Scientific Advisory Group for Emergencies (Sage), Prof John Edmunds.
The seven-day rate of new cases of Covid-19 in the UK has now risen above 20 cases per 100,000 people.
On Sunday 2,988 new cases were announced, which was the highest figure since 22 May.
Mr Jenrick told BBC Breakfast: "The virus is still very much with us, it's still concerning."
He said if people followed the government's guidance "we should be able to continue to control the virus but we're going to have to be especially cautious as we go into the autumn and winter".
"If we all play our own part then we should be able to maintain our daily lives in this sort of new normal but we've got to be very cautious because, as you've seen, the number of cases is rising."
Prof Edmunds, from the London School of Hygiene and Tropical Medicine, told ITV's Robert Peston that the R number – which rates Covid-19's ability to spread – had risen "above one", so the UK was in a "risky period".
"We can see the epidemic is taking off again. So I don't think we've hit that sweet spot where we've been able to control the epidemic and allow the economy to return to some sort of normality," he said.
Prof Edmunds, who has previously said he wished the UK had gone into national lockdown earlier than it did, added that cases were rising from a "relatively low level" but "are increasing now exponentially".
Earlier on Monday, Prof Van Tam described the latest change in coronavirus infections across the UK as a "great concern".
"People have relaxed too much. Now is the time for us to re-engage, and to realise that this a continuing threat to us," he said.
Prof Van Tam added that hospital admissions and deaths were "at a very low level" in the UK and the rise in cases was most prominent among those aged between 17 and 21 – but the country risks following the trajectory of some EU countries.
"Where case numbers rise initially in the younger parts of the population they do in turn filter through and start to give elevated rates of disease and hospital admissions in the older age groups, and we know that then becomes a serious public health problem," he said.
"The fact that 17 to 21-year-olds are not becoming ill means they are lucky, but they also forget because the disease is not severe for them that they are potent spreaders."
He said the UK would be in for "a bumpy ride over the next few months" if people did not adhere more stringently to social distancing rules.
His comments come after Health Secretary Matt Hancock warned young people that the UK could see a second spike in coronavirus cases if they don't follow the rules.
"Don't kill your gran by catching coronavirus and then passing it on," he told BBC Radio 1's Newsbeat.
Wake-up call for the public
Prof Jonathan Van Tam was known for his plain speaking at Downing Street press conferences earlier in the pandemic.
Now England's deputy chief medical officer has once again come out with a blunt warning about the spread of the virus.
Put simply, he believes there's been a significant and concerning change in recent days. No longer is this all about local outbreaks – instead, in his view, there is now a general spread of the disease in many parts of the country.
He suggests social distancing has broken down for some parts of society and points to rising case numbers amongst 17 to 21-year-olds.
That does not mean hospital admissions, currently relatively low, will definitely rise. But Prof Van Tam thinks that is very possible.
He implied the next week would be critical as officials and ministers studied the emerging data.
This is a wake-up call for the public to get real about social distancing, from a medical leader who is clearly worried.
The Sage scientists' comments come as more parts of the UK are to face tougher restrictions following a rise in the number of cases.
Stricter rules on visiting other people's homes were extended to two more areas in the west of Scotland from midnight.
In Wales, the county borough of Caerphilly is to be placed under a local lockdown from 18:00 BST on Tuesday.