Boris Johnson has said the UK is turning the tide on tackling coronavirus but is still facing a moment of “maximum risk” and he will not be forced to end the lockdown prematurely.

Speaking outside 10 Downing Street on Monday, his first day back after recovering from coronavirus, the prime minister gave businesses a stark warning to contain their impatience on easing restrictions.

He thanked the public for giving up their basic freedoms and said he understood how tough it had been, particularly on businesses, entrepreneurs and the hospitality sector, and that the economy was suffering.

However, he spoke directly to those pushing for an end to the lockdown sooner rather than later, saying it would risk a second spike of infections and a “new wave of death”.

“I can see the long-term consequences of lockdown as clearly as anyone, so yes, I entirely share your urgency,” he said. “It is the government’s urgency. And yet we must also recognise the risk of a second spike, the risk of losing control of that virus and letting the reproduction rate go back over one.

“That would mean not only a new wave of death and disease but also an economic disaster and we will be forced once again to slam on the brakes across the whole country, and whole economy, and reimpose restrictions in such a way as to do more and lasting damage.

“I want to get this economy moving as fast as I can, but I refuse to throw away all the effort and sacrifice of the British people and risk a second major outbreak and huge loss of life and the overwhelming of the NHS.”

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He asked businesses to contain their impatience and understand that while there had been success in suppressing the illness, it was still a moment of significant national risk, despite “having begun together to wrestle [coronavirus] to the floor”.

“So it follows this is the moment of opportunity, this is the moment when we could press home our advantage. It is also the moment of maximum risk,” he said.

There would be a point at which the UK could “fire up the engines of this vast UK economy”, Johnson said, but that would depend on meeting the five tests the government had set itself: the death rate falling, the NHS not being overwhelmed, the infection rate going down, getting on top of testing and personal protective equipment supplies, and avoiding a second peak of the disease.

Johnson said there would also be “maximum possible transparency” from now on, which may have been a direct response to mounting pressure on the government to release the scientific data it was relying on to make decisions, and to make public exactly who was sitting on its scientific advisory group, Sage.

The prime minister is expected to meet ministers throughout the week and regularly host the morning Covid-19 response meetings as he gets back to work since being admitted to hospital with the virus.

Earlier, the health minister Edward Argar played down speculation that Johnson was expected to ease lockdown measures before 7 May, the next date by which ministers are due to review it.

“We’re very clear at the moment the science isn’t saying we are ready to lift the restrictions that have been placed on people,” Argar said. “We’ve made huge progress, we’ve seen that curve flattened in recent weeks … but we’re not there yet.”

He said the lockdown had been working and “now is not the time to let up”.

The government’s chief scientific adviser, Sir Patrick Vallance, has said the reproduction rate of the virus was now below one (an infected person is passing it on to fewer than one other person), but Argar would not be drawn on it in a round of morning media interviews.