Experts and scientists have warned the planned relaxation of coronavirus restrictions over Christmas could lead to a spike in cases, a third wave of the pandemic and a January lockdown.

However, the mental health benefits of restrictions easing over Christmas have also been stressed, although a "balance" must be found. 

Professor Andrew Hayward, a member of the Government's Scientific Advisory Group for Emergencies (Sage) told the BBC: “Effectively what this will be doing is throwing fuel on the Covid fire. I think it will definitely lead to increased transmission. It is likely to lead to a third wave of infection, with hospitals being overrun, and more unnecessary deaths.

“We are still in a country where we have got high levels of infection with Covid, particularly in young people. Bringing them together for hours, let alone days, with elderly relatives, I think, is a recipe for regret for many families.

READ MORE: 'The virus doesn't care if it's Christmas': Leading government advisor's warning about risks of mixing over festive period

“With the vaccine on the way, if we are not very careful over Christmas we are really in danger of snatching defeat from the jaws of victory on this one.”

It comes as the British Medical Association (BMA) also warned easing of coronavirus restrictions over Christmas will “almost certainly” lead to a rise in the infection rate, as three households will be able to form a bubble over the festive period.

The UK Government and devolved administrations have agreed a temporary easing of measures which will allow three households to mix in a bubble from December 23 to 27.

Social distancing will be relaxed within the bubbles, giving people the chance to hug friends and family for the first time in months.

BMA UK council chair Dr Chaand Nagpaul said: “There is a careful balance to be struck when weighing up the risks associated with Covid-19 and the understandable wish to see loved ones this Christmas.

“This virus does not discriminate against certain days of the year.

“Relaxing the rules on indoor mixing for a five-day period will almost certainly carry the risk of a rise in infection rate and possibly more hospitalisation and deaths, adding further pressure on the health service, doctors and NHS staff.

“With infections levels and hospitalisations still worryingly high, and the daily death toll in the second wave now rising, we do not want loved ones to become seriously ill, hospitalised or lives put at risk this Christmas.

“The priority now must be to support the public to adhere to stringent rules around physical distancing and infection control to drive down the infection rates further by Christmas. The lower the level of infection the less risk it will place for families to meet at Christmas.”

Dr Nagpaul added that “it is absolutely vital” people adopt the necessary safety precautions if mixing with other households, such as ventilating rooms and limiting physical contact when masks are not worn.

Meanwhile Professor Linda Bauld, of the University of Edinburgh, has said that while there will be 'mental health benefits', people must balance the risks of getting together on Christmas.

She said: "All the way through this we've been balancing these different harms, the harm from the virus, the unintended harms from people not being treated in hospital, mental health.

READ MORE: Coronavirus Scotland: Here are the Christmas rules for Scots

"If you look at levels of anxiety and depression from the Covid social study which is done regularly, there are about 16 per cent higher now than they were in August in the summer when we were coming out of lockdown.

"There will be mental health benefits to this, let's be absolutely clear, but it's a conversation about recognising and balancing these different risks."

Prof Bauld added however that families should practise caution and recognise that gatherings over Christmas will quite likely lead to more restrictions in January.

She said: "I'm very concerned about additional cases in January, I think there will be consequences to this and we need to recognise we might have more restrictions then, but people may decide that's a price worth paying but I really hope we can do this cautiously."

Professor Devi Sridhar has said that increases in cases following Christmas mixing is "inevitable".

She said: "It’s inevitable that when you have more people mixing indoors, you have travel restrictions being lifted meaning moves from high prevalence to low prevalence areas, we are going to pay for Christmas holidays with probably a January national lockdown.

Stressing that the recent positive developments should encourage people to remain vigilant for another few weeks, Prof Sridhar asked "why risk getting infected?"

She said: "The future is bright, we have vaccines, three now which are effective, we have mass testing coming online, so why risk getting infected in the next few weeks when actually in the next few months we’ll be in a fundamentally different position and a much safer one.

"Why not rationally hold out for a few months, we’ve been in this for 10 months already, what’s another few weeks?"