THE largest education union in Europe has demanded to know why the Government is not closing schools amid the coronavirus outbreak.

Teachers and staff are asking the Prime Minister for full disclosure over his decision not to shut schools, particularly now that plans are under way to ban mass gatherings.

Boris Johnson said on Thursday that closures now could do "more harm than good", hours after Ireland announced that schools and colleges would close for a fortnight.

The Prime Minister told a press conference: “We are not – repeat not – closing schools now.

"The scientific advice is it will do more harm than good at this time, but of course we’re keeping an open view and may change this as the disease spreads.

"Schools should only close if they are specifically told to do so.”

The letter sent by the National Education Union reads: "We all want to limit and delay the spread of the coronavirus and we do think medical advice and expert scientific advice is important in this regard.

"But it is clear that such advice can have uncertainties, and that it could be crafted to target a variety of measures.

"We now see that you may take legal powers to force schools to remain open even when heads and teachers think there is good reason to close.

"In those circumstances we, as the leaders of the largest education union, believe that it is right for us to ask you for fuller disclosure of the models you have looked at, and to understand which measures you are targeting.

"We do not have the medical expertise to know what the transmissibility is between children and staff in close quarters in classrooms - but your scientists will have made assumptions about that, together with some view of the certainty of those figures.

"It is very important that we understand what the increased rate of infection is for staff and parents if schools remain open, including obviously for those with underlying health conditions themselves, or for those they care for."

The letter, from the union's joint general secretaries Mary Bousted and Kevin Courtney, adds: "We know you've expressed concerns about children not in school being cared for by vulnerable elderly grandparents, or by NHS staff who would then not be available for work.

"However, we would suggest that parents and schools would be able to work together to find solutions to that - and we would like to know if you have any modelling of such societal responses.

"Most of all we think that education staff deserve to have access to modelling of the projected spread of the virus and the projected number of fatalities in a wide variety of scenarios including in scenarios where schools are closed for different periods of time.

"Teachers and other staff would work to help a broader societal response to mitigate the effects of the virus. We know this is especially important in a country where public services and the NHS in particular have been run down for so long.

"However it is vital that you share all of the potential models you have with us if that societal response is to be as strong as possible."

Northern Ireland's administration has not introduced the same measures as the Republic of Ireland, but Deputy First Minister Michelle O'Neill said schools and colleges should be shut.

The UK total of confirmed coronavirus cases has jumped to 820 this morning, after Wales reported 22 new cases.

Boris Johnson described the outbreak of the virus as "the worst public health crisis for a generation".

He said: “I must level with you and level with the British public. Many more families are going to lose loved ones before their time.”

The Government has issued guidelines for people in self-isolation, which apply to both confirmed and suspected cases.

The website states: "It is very important that you stay at home whilst you have coronavirus (COVID-19).

"This will help to protect your friends, colleagues and the wider community and will help control the spread of the virus.

"We realise that staying at home may be difficult or frustrating."