A leading professor has warned "only about half" of people with Covid-19 "ever get tested" amid the new Omicron variant.

Professor Andrew Hayward, a member of the Scientific Advisory Group for Emergencies (Sage), made the comments on BBC Breakfast.

Speaking in a personal capacity, he said the doubling rate of Omicron would lead to an “extraordinary number of cases” and “a huge wave of infection”.

He added: “If you think about getting a year’s worth of rain over a month, then you’re going to get flooding and potentially severe flooding, no matter how much you’ve shored up your defences.

“And that’s the concern here – that that huge wave is going to cause lots of people to be off work having to isolate, which is going to cause disruption, and it’s going to spill over into people going into hospital.

“Now the rate at which it spills over is uncertain because we don’t know exactly how severe it is yet, but we’ve no particular reason to think that it’s less severe than previous strains.

“We know that Covid is always going to be less severe if you’ve been immunised but it may be that rather than the strain itself that’s making a lot of cases look less severe.”

He added: “Only about half or maybe even fewer of people who do have Covid ever get tested”.

Are Omicron symptoms more mild or severe?

Prof Hayward said more data should come around Christmas time or in the New Year on Omicron's severity.

He added: “The trouble is, if you wait until then and don’t do anything to reduce the spread, then you’re in a much worse situation than if you take some action now.”

The Sage scientist urged people to book their booster jabs and reduce contacts before the Christmas period.

Asked about whether current restrictions are geared towards Christmas, Prof Hayward told BBC Breakfast: “We know that the correct thing to do is always a balance between the impact on the economy, the impact on people’s social lives and the impact on the virus and subsequent hospitalisations.

“And so of course, in some ways that balance is slightly different at Christmas because so many people a, their income is dependent on commerce around Christmas time, particularly the hospitality sector and shops, and b, people want to socialise, so that you know the balance is different and it’s always a balance.

“However, I think the scale of the potential problem that we’re looking at here does mean that we need to bite the bullet and we need to tell people that there’s two really important things here.

“One is to get boosted, the other if we want to slow it down now… Then what we need to do is reduce the number of contacts that we have, we need to avoid crowded spaces with lots of people in and unfortunately, yes, that does mean parties etc. And so that’s a difficult message.”

Prof Hayward said he believed the communication in Scotland had been clearer than in England.

Asked if he felt the science was not being followed, he said scientists “set out what’s likely to happen, what some of the options are in order to reduce that, and it’s up to the Government’s to balance those.”