A total of 55 people in the UK have now died after testing positive for the coronavirus, Health Secretary Matt Hancock has said.
This is a rise of 19 deaths in a 24-hour period.
Making the announcement in the House of Commons, Health Secretary Matt Hancock called the coronavirus pandemic "the most serious public health emergency that our nation has faced for a generation".
Mr Hancock said: "Our goal is to protect life. Our actions have meant that the spread of the virus has been slowed in the UK and I want to pay tribute to the officials at Public Health England and the NHS for their exemplary approach to contact tracing and their work so far.
"However, the disease is now accelerating and 53 have sadly now died. Our hearts across this whole house go out to their families."
The announcement came after two more deaths - one each - in Wales and Scotland.
Earlier in the day, the Department of Health announced that as of 9am on Monday, the number of UK coronavirus cases had risen to 1,543 - up by 171 in 24 hours.
Mr Hancock added that emergency legislation will be introduced to MPs on Thursday, with the aim of giving the government new powers to keep public services on track during the outbreak.
He also said that Prime Minister Boris Johnson has spoken to manufacturers today by phone, asking them to produce much-needed ventilators for the health service.
Downing Street put out a call for the equipment over the weekend, over fears intensive care units in the NHS could soon face unprecedented demand for them.
Speaking in the first of the newly announced daily press conferences on the outbreak, Prime Minister Boris Johnson told Britons to avoid pubs, clubs, restaurants and theatres and to only make essential journeys in the "national fightback" against coronavirus.
He added that the number of coronavirus cases in the UK could double every five or six days without "drastic action".
"Today, we need to go further, " Mr Johnson said.
In Europe, European Commission president Ursula von der Leyen has proposed a 30-day ban on non-essential foreign travel to the EU. The proposal will be discussed with member states tomorrow.
An official earlier said: "Ireland and Britain are encouraged to align."
In other coronavirus developments:
A Public Health England briefing seen by Sky News claims the coronavirus could see up to 7.9 million people requiring hospital treatment in the UK over the next 12 months.
The document also confirms that healthcare workers who have symptoms of COVID-19 would not necessarily be tested.
Chief medical officer Chris Whitty has previously said up to 80% of the population could catch the virus in a worst-case scenario.
On Sunday, the Health Secretary Matt Hancock said the elderly could be asked to self-isolate for up to four months.
Transport Secretary Grant Shapps said on Monday that people over the age of 70 will be asked to self-isolate "as and when the moment is right" - but that they would still be able to go outside and "walk the dog".
He said: "We will ask people to do that as and when the moment is right."
Those who refuse to self-isolate or fail to comply with restrictions could face a fine of up to £1,000.
Education Secretary Gavin Williamson is due to meet school leaders to discuss the implications of closing schools and postponing exams.