Coronavirus in Yorkshire: New guidelines urge anyone in household with symptom sufferers to self-isolate

Mr Johnson said "if you or anyone in your household" had one of the two symptoms - a high temperature or continuous cough - "you should stay at home for 14 days".

He said: "That means that if possible you should not go out, even to buy food or essentials, other than for exercise and in that case at a safe distance from others.

"Now is the time for everyone to stop non-essential contact with others and to stop all unnecessary travel."

The Prime Minister said that according to the Scientific Advisory Group for Emergencies (Sage) "it looks as though we are now approaching the fast growth part of the upward curve" in the number of cases.

He said: "Without drastic action cases could double every five or six days."

Mr Johnson said by the weekend, groups particularly vulnerable to Covid-19 will be asked to stay at home for 12 weeks.

He said: "In a few days time, by this coming weekend it will be necessary to go further and to ensure that those with the most serious health conditions are largely shielded from social contact for around 12-weeks.

"Again, the reason for doing this in the next few days rather than earlier or later is that this is going to be very disruptive for people who have such conditions."