Professor Stephen Powis, NHS England's medical director, said the NHS could start testing hundreds of thousands of people per day for Covid-19 within a matter of weeks.

Prof Powis said he wanted to "ramp up" the tests within the next few weeks. 

He said: "We want to get hundreds of thousands of tests ramped up in the next few weeks per day."

Asked to clarify whether he really meant hundreds of thousands of tests per day, Prof Powis said: "That's what we are aiming for.

"That is what we want to ramp up to, but remember this is a new virus and we're starting from scratch.

"The kits which are required to do this testing are being manufactured as we speak. We are getting those into the country, we are ramping it up.

"I am talking of hundreds of thousands of tests.

"All of this is ramping up and increasing as we speak but yes, you heard me correctly, we need to get to hundreds of thousands of tests a day, and we will do that over the course of the next few weeks and we will be making tests available to NHS staff within the next few days."

Prof Powis also told BBC Breakfast there have been "outbreaks of altruism and people wanting to help", adding he has been "bowled over" by medics returning to the front line and the response from people signing up to help those in need.

On Wednesday, Health Secretary Matt Hancock called for 250,000 people to sign up as volunteers.

Prof Powis said: "Overnight 170,000 people have signed up - that's three a minute to help the NHS.

"It's an absolutely astonishing response."

But the top medic said people must play their part by adhering to the instructions laid down by the Prime Minister.

He said: "When I see groups of 20 having a BBQ, frankly this putting pressure on our NHS, it is potentially costing lives and it means we need more ventilators.

"That just has to stop, that behaviour has to stop. You are putting untold pressure on the NHS by that behaviour."