A test to find out whether people have been infected with coronavirus in the past has been approved by health officials and is likely to be rolled out to frontline workers first.

Public Health England (PHE) said the antibody test, developed by Swiss pharmaceutical giant Roche, was a “very positive development” after experts at its Porton Down facility gave it the green light.

The test – which Prime Minister Boris Johnson has previously called a “game-changer” – picks up 100% of cases where somebody has had coronavirus in the past.

Experts believe those who have had Covid-19 develop a degree of immunity, meaning the test could prove a useful tool for helping to ease lockdown restrictions.

Number 10 said the new antibody test would “certainly” be available on the NHS but commercial discussions with Roche are ongoing.

The Prime Minister’s official spokesman said the idea of an “immunity certificate” was still under consideration if science showed that people developed immunity to Covid-19.

Professor John Newton, national coordinator of the UK Coronavirus Testing Programme, said although it was still unclear to what extent the presence of antibodies indicated immunity, the test was a “very positive development”.

He added: “Last week, scientific experts at PHE Porton Down carried out an independent evaluation of the new Roche Sars-CoV-2 serology assay in record time, concluding that it is a highly specific assay with specificity of 100%.

“This is a very positive development because such a highly specific antibody test is a very reliable marker of past infection.

“This in turn may indicate some immunity to future infection, although the extent to which the presence of antibodies indicates immunity remains unclear.”

Roche said it could supply hundreds of thousands of the tests each week. The tests run on fully-automated equipment already widely installed by Roche at NHS sites across the UK.

The pharmaceutical firm said it would prioritise tests for distribution via the NHS before looking at how they may be sold to individuals.

Professor Sir John Bell, regius professor of medicine at Oxford University, said the development of the antibody test was “a good result”.

He told Radio 4’s Today programme: “It’s a step in the right direction. In the evolution of these antibody tests to get one that works really well is a major step forward.”

Sir John said antibodies “stick around probably for a year or two” adding that the Roche test was the “best approved test available on the market now.”

But he said it was currently unclear whether having Covid-19 gave immunity against all future infection with the virus.

“What I think you can’t for absolutely for sure say is that you would be protected in the future,” he said, adding there were still improvements that could be made to antibody tests.

Health minister Edward Argar said the Government intends to roll out the new test to frontline workers first.

Speaking on BBC Breakfast, Mr Argar said: “We’re in discussion at the moment with Roche on this.

“It’s only just gone through the Public Health England assessment as being reliable, as doing the job, and therefore we are having those discussions.

“But we are keen to get as many as quickly as we can and get them out, primarily to the frontline first, the NHS, social care and then more widely.

“Because this really will be – as the Prime Minister said – this has the potential to be a game-changer.”

Mr Argar stressed that the public could not yet get their hands on the test, saying: “We’re not in a position yet to roll it out to the public and have those tests ready to go.”

News of the test comes as:

– Communities Secretary Robert Jenrick admitted the situation in care homes was “absolutely terrible” as the Government prepared to set out more details on how a £600 million package for infection control will be spent in England

– Some 126,064 tests were carried out on Wednesday.

– Data published by NHS England showed 0.9 million A&E attendances were recorded in April 2020, down 57% from 2.1 million in April 2019

– An average of 148,000 people in England had Covid-19 between April 27 and May 10 (lockdown period), according to new estimates by the Office for National Statistics – the equivalent of 0.27% of the population.

A Department of Health and Social Care spokeswoman said: “We are exploring the use of antibody testing across the NHS and ultimately the wider public.

“We are delighted that devices are progressing through validation, and are actively working on our plans for rolling out antibody testing and will make announcements in due course.”

The findings come as former Health Secretary Jeremy Hunt said it was “pretty clear now” that community testing should not have been abandoned on March 12.

The chairman of the Commons Health and Social Care Committee said the Government was “getting excellent scientific advice” but asked why the Scientific Advisory Group for Emergencies (Sage) “didn’t model the South Korean test, track and trace approach that we are now adopting right at the beginning?”.

In a frank admission, he also said the Government had not thought enough about the importance of testing – including for care homes – during his years as health secretary.

He said: “I think the practical thing that we can all see needed to have happened was to make sure that everyone discharged from hospitals into care homes was tested for Covid before they were sent to a care home,” he told BBC Radio 4’s Today programme.

“But because we didn’t have that testing capacity at the time, it wasn’t possible to do that.

“In retrospect, and I have responsibility for this as someone who was health secretary for six years, because we were over-focused on pandemic flu, and not on pandemic SARS-like viruses, we haven’t been thinking for some time about the importance of testing.”

Mr Hunt said it was taking “much too long” for the current Covid-19 tests results to be processed.

“If you call up because you have got Covid symptoms, you really need test results back in 48 hours,” he said.

“Within that window, we need to contact everyone who you have been near in the last three or four days.

“That’s really got to happen very, very fast, otherwise there’s no point.”