Nicola Sturgeon has defended the SNP’s handling of Margaret Ferrier’s rule-breaking Commons visit and train journeys between Glasgow and London while suffering coronavirus symptoms.

Scotland’s First Minister said she could not understand Ms Ferrier’s “flagrant, and dangerous breach of the rules” but said the SNP had acted quickly and “appropriately” when party members learned the details.

Opposition politicians have demanded answers to what the SNP knew about Ms Ferrier’s symptoms and infection and the party’s response.

Ms Ferrier admitted she was tested for coronavirus on Saturday after developing symptoms but still took a train to Parliament on Monday when she should have been self-isolating.

The Rutherglen and Hamilton West MP gave a four-minute speech in the House of Commons at 7.15pm on Monday during a debate on coronavirus.

Ms Ferrier said she received her positive test result that same evening – although it is not known if this was before or after speaking in Parliament.

She then took a train back to Glasgow.

Pressed on the subject at the Scottish Government’s coronavirus briefing, Ms Sturgeon said she only found out about Ms Ferrier’s actions after First Minister’s Questions on Thursday afternoon.

She said she believed the SNP at Westminster was told about Ms Ferrier testing positive for coronavirus on Wednesday but was not aware she already had symptoms and had taken a test before attending Parliament.

“It was not until yesterday my colleagues in the House of Commons realised the circumstances – that she’d actually taken the test before travelling to London and then travelling back having been told that she was positive,” Ms Sturgeon said.

After being informed, Ms Sturgeon said she was “struggling to comprehend how anybody could have acted in that way” and was anxious to understand all the facts.

Ms Ferrier referred herself to the police and informed people close to her about her infection before releasing a statement on Thursday afternoon, Ms Sturgeon said.

The SNP’s Westminster leader, Ian Blackford, spoke to Ms Ferrier after flying into Inverness on Thursday afternoon and announced that evening that the party whip had been withdrawn.

Asked about her party’s handling of the situation, Ms Sturgeon said: “I think the SNP has acted quickly, appropriately and, actually, we have not tried to protect a colleague here.

“We’ve tried to do the right thing, given the circumstances we’re dealing with.”

Shadow Scottish Secretary Ian Murray has written to Mr Blackford demanding answers about Ms Ferrier’s “catastrophic, negligent actions” while she had coronavirus symptoms and after testing positive.

Mr Murray’s letter asks 23 questions about the timeline of Ms Ferrier’s coronavirus test and subsequent positive result, details of when SNP leaders, chief whip and party staff knew of her infection, and the MP’s contact with colleagues and parliamentary staff.

Mr Murray said: “These revelations have caused a great deal of confusion and concern within Parliament.

“We are faced with catastrophic, negligent actions by an MP which have put lives at risk.

“You and your party’s slow response leaves much to be desired, and the party must come forward with a full and clear explanation.”

Ms Sturgeon, speaking at the briefing, said Ms Ferrier has now “fully co-operated” with the UK’s Test and Trace system, adding: “People who might have been in contact with her have all been properly identified and contacted.”

Prior to Ms Sturgeon’s comments, Scottish Conservative leader Douglas Ross accused the SNP of “treating the public like fools” and suggested their timeline “is full of holes”.

Mr Ross said: “The SNP say they only found out about any wrongdoing on Thursday. That means we’re supposed to accept that the SNP found out Margaret Ferrier tested positive on Wednesday – and asked nothing.

“The public is expected to believe SNP bosses didn’t think to ask a single question, not one, about when she tested positive, where she had been or who she had been around, despite her appearance in the Commons earlier that week.”

Scottish Liberal Democrat MSP Alex Cole-Hamilton said: “Margaret Ferrier spent her time in London attending Parliament alongside her colleagues.

“She could have put any number of them at risk and they in turn could have been unwittingly risking the lives of their own constituents once they too return to Scotland.”

He added that the SNP “need to apologise to the rail staff and members of the public who have been put at risk by Margaret Farrier’s reckless decision to travel”.