Boris Johnson's visit to Scotland to promote the Union is "absolutely essential", Cabinet member Michael Gove has insisted after First Minister Nicola Sturgeon questioned whether the trip is necessary during the pandemic.
Amid signs of rising support for Scottish independence, the Prime Minister is visiting Scotland on Thursday to argue that the Union has been integral in administering the Covid-19 vaccine, providing coronavirus testing and giving economic support.
He donned PPE on a visit to the Lighthouse Laboratory at the Queen Elizabeth University Hospital campus in Glasgow, where coronavirus tests are processed.
Ms Sturgeon said Mr Johnson's visit to Scotland is "not essential" during the current lockdowns, arguing that politicians have a "duty to lead by example" as the public live under strict restrictions.
There are growing concerns in Westminster about support for Scottish independence, as Ms Sturgeon argues there would be grounds for a new referendum if her SNP party wins a majority in the Holyrood elections scheduled for May.
Ahead of the visit, Cabinet Office minister Mr Gove told BBC Radio Scotland: "He's the Prime Minister of the United Kingdom, it's absolutely essential that the Prime Minister is there to see how on the front line we are progressing in our vaccine delivery and rollout programme.
"It's critically important that the Scottish Government and the UK Government are working together to do everything we can to support the rollout and see what we can do to improve it."
Mr Gove insisted there is "no substitute for a leader better than being there", when questioned why he did not speak to people remotely.
He said the visit will present "no danger to anyone's health", adding "the Prime Minister will be operating in a Covid-secure way".
Labour leader Sir Keir Starmer also backed the Prime Minister's visit, insisting he had a right to see what was happening in all parts of the UK.
Sir Keir told LBC Radio: "I'm with the Prime Minister on this one.
"He is the Prime Minister of the UK.
"It's important that he travels to see what is going on, on the ground."
But concerns have been raised that Mr Johnson may not be the best figure to champion the Union, with polls suggesting support has risen amid a backdrop of the coronavirus pandemic and of Brexit, a campaign the Prime Minister fronted, while Scotland backed remaining in the EU.
Mr Gove insisted on BBC Breakfast that the Prime Minister is "a huge asset" for the Union, when challenged over his handling of Brexit and Covid-19.
Downing Street, which has insisted it is key for Mr Johnson to remain "visible" as the "physical representative" of the UK Government, plans to stress the benefits for Scotland of being in the UK.
Officials said Westminster has delivered more than one million rapid lateral flow test kits to Scotland so far and is funding testing sites across the country – including seven drive-through centres, 27 walk-in sites and 21 mobile testing units, along with the Lighthouse Lab in Glasgow.
Westminster cash has provided 62% of testing kits in Scotland, No 10 added.
Speaking ahead of his visit to Scotland, the Prime Minister said: "Mutual co-operation across the UK throughout this pandemic is exactly what the people of Scotland expect and it is what I have been focused on.
"The people of the UK have stood together during this pandemic: from our doctors and nurses in our hospitals to our shop workers, scientists, lorry drivers and teachers – working together as one truly United Kingdom is the best way to build our Covid recovery."
But SNP deputy leader Keith Brown said the Prime Minister's trip is evidence that he is in a "panic" about the prospect of another referendum.
The MSP said: "Clearly, Boris Johnson is rattled. By branding this campaign trip as 'essential', this is clearly a Prime Minister in panic, who knows the Tories are losing the argument on independence.
"Twenty polls in a row have shown that a majority of voters believe Scotland's future should be in Scotland's hands – not Boris Johnson's."