BORIS Johnson will take the lead at today’s Downing St press conference, No 10 confirmed, as Nicola Sturgeon insisted that his chief aide Dominic Cummings should go.

The First Minister  drew a comparison to the resignation of Catherine Calderwood as Scotland's Chief Medical Officer after she visited her second home twice earlier in the crisis.

Ms Sturgeon tweeted: "I know it is tough to lose a trusted adviser at the height of crisis but when it's a choice of that or integrity of vital public health advice, the latter must come first.

"That's the judgement I and, to her credit, Catherine Calderwood reached. PM and Cummings should do likewise."

The row over Mr Cumming's decision to travel 250 miles from London to Durham during the lockdown has thrown into question the Prime Minister's own credibility as well as the integrity of the UK Government’s coronavirus advice.

Conservative MPs piled the pressure on their party leader by breaking ranks to say that the chief aide should go after he travelled 250 miles from London to Durham during the lockdown.

The Prime Minister’s decision to appear at the daily briefing - pushed back an hour until 5pm - followed calls from Labour and the SNP for him to “come out of hiding” and explain fully the actions of Mr Cummings.

He has insisted he behaved “legally and reasonably and legally”. It is believed Robert Jenrick, the Communities Secretary, had been pencilled in to take the press conference.

This morning, the chief aide arrived at No 10, casting an aggrieved look at waiting cameras, just hours before the daily Downing St briefing.

Steve Mr Baker, the former Brexit minister and a leading Leave campaigner, told Sky's Sophy Ridge On Sunday programme: "If he doesn't resign, we'll just keep burning through Boris's political capital at a rate we can ill afford in the midst of this crisis.”

His Tory colleague, backbencher Sir Roger Gale, said while he appreciated Mr Cummings's desire to protect his child, there could not be one law for the Prime Minister's staff and another for everyone else. "He has sent out completely the wrong message and his position is no longer tenable."

READ MORE: Dominic Cummings row: Here's everything you need to know 

Conservative Brexiteer Peter Bone declared: "When an adviser becomes the story, the adviser has to go. Boris Johnson can carry on without Dominic Cummings if he goes but it will be hard if he stays."

Labour and the SNP are demanding an urgent top-level inquiry into the row and the opposition parties urged the PM to take this afternoon’s daily Downing St press conference to answer questions directly. But it is reported Mr Johnson is adamant he will not throw Mr Cummings "to the dogs".

The chief aide has insisted he acted "reasonably and legally" and had done the "right thing".

At the start of this afternoon's Scottish Government press briefing in Edinburgh, Jeanne Freeman, Scotland's Health Secretary, was keen to underline the lockdown message on self-isolation, saying the "message may have become confused in the last 24 hours because of events in other parts of the UK" and stressing that it meant that anyone with the virus "should not leave the house for any reason".

Despite the growing furore, Grant Shapps, the Transport Secretary, insisted Mr Cummings would not resign but, as he took the Sunday morning media round for the Government, admitted he had not spoken to him in person about the growing controversy.

Asked if the Government’s guidelines, which state “if you or someone you live with has symptoms of coronavirus, do not leave your home for any reason,” still applied, Mr Shapps said: “Absolutely right, the advice does stand.”

However, he then referred to what has been described as “wriggle room,” pointing out how a section in the guidance, recognised that if people were living with children, then ‘not all of these measures will be possible’.

When it was put to the minister that Mr Cummings had broken the rules, the Secretary of State explained: “The guidance also makes clear you have to put in place the structures around to look after, in this case, a four-year-old…[who] needs to get support and having that support around them, in this case, by being not with the parents but in the property adjacent to the parents with the support of the sister and a niece meant they could bring food to the house and so forth.”

On Saturday, Jenny Harries, England’s Deputy Chief Medical Officer, said everyone with the virus should self-isolate unless there was a risk to life.

Pressed by the BBC's Andrew Marr on whether there was such an extreme risk to life, Mr Shapps replied: "A four-year-old can't feed themselves, a four-year-old can't bathe themselves and change their clothes, so it is clear they wanted to put some measures in place."

The lockdown began on March 23. On March 30, No 10 confirmed Mr Cummings had the coronavirus and was self-isolating. A day later Durham police said it had been "made aware of reports that an individual had travelled from London to Durham and was present at an address in the city".

On April 5, the Guardian and the Mirror were told by an unnamed neighbour that Mr Cummings was seen in his parents’ garden in Durham. A week later, Robin Lees, a 70-year-old retired chemistry teacher, claimed he saw Mr Cummings walking at Barnard Castle, 30 miles away.

READ MORE: Tory MPs break cover and call for Dominic Cummings' resignation over lockdown trip

On April 14, the Downing St aide returned to work. But five days later, an unnamed witness claimed to have seen Mr Cummings walking with his wife in Durham, recognising him by his trademark beanie hat and overhearing him remarking that the bluebells were "lovely".

The second trip to Durham was “untrue,” insisted Mr Shapps, while Downing Street made clear it would "not waste time" replying to the fresh allegations from "campaigning newspapers".

As the row built, it was conspicuous that Nicola Sturgeon had made no comment on it instead taking to Twitter this morning to ask the public to "stick to lockdown rules".

However, her SNP colleague Kirsty Blackman said: “The Tory Government now has serious and growing questions to answer about Dominic Cummings' rule-breaking and the Downing Street cover-up.

"Despite having eight weeks to get their story straight, the excuses are just not credible and do not stack up. This is now an issue of Boris Johnson's judgment and integrity.

"A mounting rebellion of Tory MPs have joined calls for Dominic Cummings to go. They understand the lasting damage this is doing to public confidence in the Tory Government and its Covid-19 response.

"The longer Mr Cummings stays in place, the more he will undermine the Tory Government's credibility and the more people will question the Prime Minister's judgement," added the Aberdeen MP.

Meanwhile, Devi Sridhar, Professor of Global Public Health at Edinburgh University, also called for Mr Cummings to resign.

Speaking on the Sophy Ridge show, she said: "He undermined the core public health message which was to stay home, to make sure that children are not left with elderly relatives and also going from an area that was ahead of the country - London - to an area that was a bit behind, north-east England.

"North-east England is now one of the hardest hit parts of the country. So, the clear thing is, yes, he needs to resign, but we also need to move on and bring focus to the key issues facing the UK."

Prof Sridhar pointed out how the UK now had close to 60,000 excess deaths, one of the worst death rates per capita in the world.

"We don't have a good way out of this lockdown because there is no testing and tracing infrastructure to let us safely lift the lockdown and we have a lot of people suffering because of a lack of clear strategy of how we are going to move forward and get out of the deep hole that we are in," she added.