Nearly 3,000 new cases of Covid-19 have been reported in the UK in the largest daily figure since May, with Health Secretary Matt Hancock admitting the rise is "concerning".
Government figures show there have been a further 2,988 lab-confirmed cases of coronavirus in the UK as of 9am on Sunday.
This brings the total number of confirmed cases in the UK to 347,152.
Sunday's figure is the highest since May 22 when 3,287 cases were recorded, and is also the first 24-hour period when cases passed 2,000 since the end of May.
The tally was an increase on Saturday's figures of 1,813 new cases.
Scotland recorded 208 new coronavirus cases, the highest daily increase in positive tests for more than 17 weeks.
The last time more people tested positive for Covid-19 in Scotland was May 8, when there were 225 new cases of infection.
Mr Hancock described the UK figures as "concerning".
He told Sky News: "The cases are predominantly among younger people, but we've seen in other countries across the world and in Europe this sort of rise in the cases amongst younger people leading to a rise across the population as a whole.
"It's so important that people don't allow this illness to infect their grandparents and to lead to the sorts of problems that we saw earlier in the year."
Shadow health secretary Jonathan Ashworth said: "Today's increase in coronavirus cases is deeply concerning and a stark reminder that there is no room for complacency in tackling the spread of the virus.
"This increase, combined with the ongoing testing fiasco where ill people are told to drive for miles for tests, and the poor performance of the contact tracing system, needs an explanation from ministers.
"Matt Hancock must come to the House of Commons tomorrow to set out what is being done to get testing back on track and bring case numbers down."
Yvonne Doyle, medical director at Public Health England, said most of the new cases are people tested in the community and that the situation was being monitored.
She said: "There were broad increases in cases of Covid-19 across England and although no single area accounts for the overnight change, Birmingham had the largest increase in overnight cases and the majority of new cases were in the north of England.
"This is a reminder of the continued risk from this virus. People should continue to follow social distancing rules, wash their hands regularly and wear a face covering in enclosed spaces."
Despite the sharp increase in cases, the number of deaths has not increased in kind.
On Sunday, the Government said 41,551 people had died in the UK within 28 days of testing positive for Covid-19 as of Sunday, an increase of two on the day before.
Paul Hunter, a professor in medicine at the University of East Anglia, expressed particular concern over the increase as figures are typically lower on a Sunday.
He said: "Some of that increase may be because of catch-up from delayed tests over the past few days due to the widely reported difficulties the UK testing service has faced dealing with the number of tests being requested.
"Nevertheless, this represents a marked increase in the seven-day rolling average of 1,812 cases per day compared to 1,244 a week ago and 1,040 a week before that.
"Fortunately, the daily reported numbers of deaths due to Covid-19 remain very low, with a seven-day rolling average of just seven deaths per day.
"However, with the new approach to recording deaths, it is difficult to be confident that there are timely statistics.
"Sadly it is beginning to look like we are moving into a period of exponential growth in the UK epidemic, and if so we can expect further increases over coming weeks."