The First Minister tore into the Rutherglen and Hamilton West MP’s actions during today’s Scottish coronavirus briefing.
She was speaking less than 24 hours after Ms Ferrier admitted breaking coronavirus rules by travelling between Glasgow and Westminster, having tested positive for Covid-19.
In an emotion-charged conference, Ms Sturgeon labelled Ms Ferrier’s actions “flagrant and dangerous”.
She said: “She accepts she made a very serious mistake and error of judgement and is not trying to evade responsibility. But can she give me a cogent explanation? No.
“Travelling on a train after testing positive is probably the worst breach possible.
“I can’t excuse it and I’m not going to try to excuse it.”
Ms Sturgeon repeatedly praised the MP as a “friend and a colleague”, but also made clear Ms Ferrier’s position was untenable.
She said: “I wish her a speedy recovery from Covid-19, but none of that changes the fact that her actions were reckless, dangerous and completely indefensible.
“I feel very angry on behalf of all of you.
“Every single day I stand here and I ask you to make horrendous sacrifices as part of our collective effort against Covid and it's really important whether you are with me or not that you can have confidence in the advice I give you.
“The rules apply to everyone, regardless of who you are.”
Ms Ferrier was tested for coronavirus on Saturday after developing symptoms, but took a train to Parliament on Monday when she should have been self-isolating.
She then gave a four-minute speech in the House of Commons on Monday night where she praised the NHS.
The very same evening Ms Ferrier received her positive test result before taking the train back to Glasgow in a flagrant violation of the laws.
Ms Ferrier has now reported herself to the police and faces a £4,000 fine if her actions are deemed “reckless".
Ms Sturgeon confirmed the SNP whip had been withdrawn from the MP, which she described as “the most serious sanction a part can impose on an elected representative”.
However, the FM suggested things should go further and called for the disgraced MP to stand down.
She explained: "I've also spoken to her directly and made it crystal clear to her that I think she should now resign as an MP.
"I did so with a heavy heart - she is a friend & colleague - but her actions were dangerous and indefensible.
"I don't have the power to force an MP to sit down, no party leader has that power.
"But I can make my views known and - difficult though it is - I have done so, and I hope she will come to the right decision in the interest of the overall integrity of the vital public health messages."
Ms Sturgeon also pointed towards the hypocrisy of some Conservatives, who criticised Ms Ferrier, but stayed silent when Prime Minister’s chief adviser Dominic Cummings breached the restrictions.
She pointed to those full of "self-righteous anger" who "completely lost their tongue when a certain special adviser in London broke the rules".
Ms Sturgeon said it was easy to criticise a political opponent, but the “real test” was criticism of friends and colleagues.
The FM also suffered a verbal gaffe during her briefing, calling the Rutherglen and Hamilton West MP “Margaret Covid” in an unfortunate mix-up.
The declarations from Ms Sturgeon came on a day the House of Commons Speaker also made his own rare intervention, branding Ms Ferrier’s actions as reckless.
Sir Lindsay Hoyle said: "This is a dangerous, dangerous thing to do.
"I would expect the member to consider what they have done, and the reckless behaviour, and how that looks to the rest of the country.
"This sends all the wrong messages. People have really got to consider their position on that.
“This was a silly thing to do, it was reckless, but to put people at risk, whether that’s in Parliament or on public transport, is not acceptable."
Sir Lindsay made clear he did not blame the SNP for the mistake, but Ms Ferrier herself.
DUP MP Jim Shannon is now self isolating after sitting on the same dining table as Ms Ferrier on Monday.
The SNP Westminster leader Ian Blackford today also suggested Ms Ferrier should stand down, but admitted he had now power to force her out.
He said: “I would say to her that her position isn’t tenable, given the circumstances that we’re in, and she has to accept her own responsibilities of what she must do.
“It’s important that it is beyond reproach that everybody, absolutely everybody, must obey the rules and we have to think about the signal that gives the public and the sacrifices that people are having to make, and it’s in the light of that that Margaret will have to do the right thing.”
She was also criticised by the leader of the Scottish Liberal Democrats Willie Rennie, who suggested it could harm public compliance with the restrictions.
He said: “Whether it's Catherine Calderwood, or Dominic Cummings, or now Margaret Ferrier, it just chips away at the coherence of the message with the public.
"They say if they can get away with it, why do we need to comply with the rules and that is crippling.
"That's why it's important she resigns, and if she doesn't she should be removed through the recall procedure.”