The number of people who have died after testing positive for coronavirus has risen to 144 in the UK, an increase of 40 per cent in a day, the government has said.

The Department of Health and Social Care has also announced there are 3,269 confirmed cases of Covid-19 in the UK, as of 9am on Thursday, after an increase of 643 cases.

​Earlier in the day, NHS England reported 29 patients had died in England after being infected with the virus.

"Patients were aged between 47 and 96 years old and had underlying health conditions," a statement from the NHS said.

"Their families have been informed."

More than 56,000 people had been tested for Covid-19 in England, as of Wednesday, with 53,595 people testing negative for the virus.

The new figures came as the UK government’s top scientific advisers warned young people not to be complacent over Covid-19 as they urged the public to follow social distancing measures.

Professor Chris Whitty, England’s chief medical officer, said the vast majority of people in all age groups would recover from the virus but warned it was a mistake for young people to assume they would “breeze through” the pandemic.

Sir Patrick Vallance, the government’s chief scientific adviser, has said everyone must now follow public health advice and socialising in pubs and clubs must stop.

“It is clear that children get this disease much less strongly than adults, I think the data on that is pretty strong now,” Professor Whitty said at a press conference on Thursday.

“But there are also some young people who have ended up in intensive care or who have ended up with severe disease around the world."

He added: “I think it's important that we don't give the impression that every single person who is young and healthy is just going to breeze through this.”

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Professor Whitty added that it was important for people to understand Covid-19 would not be a “trivial infection” for everyone.

On Monday, the government advised the British public to avoid all nonessential social contact and travel due to the outbreak.

Sir Patrick urged people on Thursday to follow the measures, as they would not have an effect unless everyone followed them.

“What we absolutely shouldn't encourage is the idea that young people somehow can ignore it because they are going to be fine,” he said.

“The mixing in pubs and restaurants and so on that is part of allowing the disease to spread needs to stop and it needs to stop among young people as well as older people.”