Professor Paul Boyle, vice-chancellor at Swansea University urged ministers to “put some thought into this as soon as possible.”

“We are going to have to think carefully about all the implications of this,” he said. “How we will manage the large number of students we have made offers to? This is such a radical change compared to what we are used to.”

Alistair Jarvis, the chief executive of the vice-chancellor membership group Universities UK, warned that no students should miss out on places at university "because of the challenges posed by the pandemic".

He added: "We await further information following the announcement that school exams will not go ahead.

"We are committed to working closely with the government, Ucas, examination regulators and school leaders on the practical implications of this and hope there will be clarity on this for students, parents, teachers and university admissions staff as soon as possible."

Clare Marchant, chief executive of Ucas, said that “flexibility” in university admissions will be “enhanced and extended to deal with the coronavirus outbreak”.

She added: “We are confident that our team and systems are ready to adapt throughout the spring and summer.

“As soon as any changes are confirmed, students will be emailed to explain how this might affect them, so it’s important they keep their email address up to date in Track.”

Schools have been ordered to shut on Friday for all but the most vulnerable and the children of “key workers”, which will include NHS workers, delivery drivers and the police.

But on Thursday evening headteachers were still waiting to be told by the Government exactly which professions will be classed as “key workers” and how the system will work in practise.

Schools have started to send out surveys to parents asking them what their job is and whether they would like to take up the offer of a school place. But there was confusion among families about whether one or both parents needed to be a key worker to qualify for a school place, and no official advice has been published on this so far.

The Daily Telegraph understands that school places will operate on a priority system. Children who have both parents classed as “key workers” or those from a single-parent family where their one parent is a key worker will be at the top of the list. Lower down will be children who have one parent classed as a key worker, and another parent who could look after them.

“If seems likely the situation goes on for many weeks, we will be able to take a more strategic look at evening it out and refine the processes,” said Julie McCulloch of the Association of School and College Leaders. “But getting things up and running for next week, there will inevitably be some compromises.”

She said that school are “to an extent doing this blind” until they are given more detailed official advice, adding that headteachers “urgently” need a definition of key workers.