A UK Government adviser has lauded Nicola Sturgeon for having the "moral courage" to make tough decisions on Covid restrictions.

Stephen Reicher, professor of psychology at the University of St Andrews and a member of government advisory body the Scientific Pandemic Insights Group, tweeted his support of the First Minister on Tuesday.

It came after Sturgeon announced new restrictions are set to come into force from Boxing Day.

They include limiting the number of people who can attend public events.

READ MORE: Nicola Sturgeon announces new Covid restrictions for Scotland

For indoor standing events, the limit will be 100, for indoor seated events it will be 200, and for outdoor events, it will be 500 seated or standing.

Reacting to the new Covid rules, Reicher said: "Thank God someone is listening to the science and has the moral courage to say the things that all of us wish weren't true, do the things all of us wish didn't need to be done, but which have to be done in order to avoid much worse."

It comes as scientists warned Boris Johnson that "dither" in imposing new Covid curbs on social gatherings and travel ahead of the Christmas weekend will cause the highly transmissible Omicron variant to spread rapidly throughout the country.

The Prime Minister delayed new coronavirus rules in England despite warning from advisers of an impending wave of infections that threatens to overwhelm the NHS.

After a lengthy Cabinet meeting on Monday, Johnson emerged to announce there would be no new changes to Covid rules.

The National: Prime Minister Boris Johnson during a media briefing in Downing Street, London, on coronavirus (Covid-19). Picture date: Wednesday December 15, 2021. PA Photo. See PA story HEALTH Coronavirus. Photo credit should read: Tolga Akmen/PA Wire

Boris Johnson has decided to stick to England's current rules

It marks a contrast between the approaches of the UK Government and the devolved administrations, which have tightened coronavirus restrictions in response to Omicron.

England, for now, will stick to its Plan B restrictions voted through earlier this month, which saw vaccine passports required for nightclub entry and football matches.

The First Minister announced the rules on Tuesday as Omicron spreads across Scotland.

On Monday, Scotland recorded its highest test positivity rate since January this year.

The National: Nicola Sturgeon was praised by a UK Government adviserNicola Sturgeon was praised by a UK Government adviser

Announcing the restrictions, Sturgeon said: "This will, of course, make sports matches, including football, effectively spectator-free over this three week period.

"And it will also mean that large-scale Hogmanay celebrations - including that planned here in our capital city - will not proceed.

"I know how disappointing this will be for those looking forward to these events, and for the organisers of them."

Businesses have warned about the impact the new restrictions will have on already struggling firms.

READ MORE: Football fans and hospitality firms react to new Covid restrictions

But Sturgeon said it is not a competition between public health and the economy.

She said: "If we don’t stem the spread of the virus, both health and the economy will suffer."

Last week, Sturgeon announced £100 million taken from existing budgets that will be used to support affected sectors.

The UK Treasury also announced a figure of £440m extra money to be used for Covid support, but the First Minister said that much of this is not new money and has already been accounted for within the Scottish Budget and re-allocating it now would cause "significant shortfalls" elsewhere, including the health budget.