Mhairi Black is stepping down as an MP at the next election.
The SNP Deputy Westminster leader said on Tuesday afternoon that Westminster is a “toxic workplace” that has taken its toll on her "body and mind".
Black's announcement is the latest in an "exodus" of SNP MPs. She is now the sixth to announce that they will not be standing for re-election.
The Daily Record understands several other MPs are still to announce that they will be standing down.
Black came to prominence in 2015 when she became the UK's youngest MP for hundreds of years - aged just 20.
In a big scalp for the SNP, she took the Paisley and Renfrewshire South seat from then Labour shadow foreign secretary Douglas Alexander.
Black told The News Agents host Emily Maitlis: "I suppose I wanted to be able to have a human conversation about why I've made the decision not to stand at the next general election.
"And I thought there is no better person to have a conversation with than yourself... I'm stepping down at the next general election."
Asked why she made the decision, she said: "Honestly, because I'm tired, is a big part of it. And the thing that makes me tired is Westminster.
"I think it is one of the most unhealthy workplaces that you could ever be in. It's a toxic environment.
"Just the entire design of the place and how it functions is just the opposite of everything that I find comfortable...
"It's definitely a poisonous place. Whether that's because of what folk can get away with in it or the number of personal motivations and folk having ulterior motives for things, and it's just not a nice place to be in.
“Whether that’s because of what folk can get away with in it or the number of personal motivations and folk having ulterior motives for things, and it’s just not a nice place to be in.”
Black follows former SNP deputy leader Stewart Hosie, former Westminster leader Ian Blackford, ex-party treasurer Douglas Chapman and fellow MPs Peter Grant and Angela Crawley in announcing that she will not stand for re-election.
She was the youngest MP since 1832 when she was elected in 2015. The Paisley-born politician was still studying at the University of Glasgow at the time.
She had to ask then-SNP Westminster leader Angus Robertson for special permission to study and sit her final exams.
Black was the House of Commons' youngest MP until 2019, when Labour's Nadia Whittome was elected. She is still the SNP's youngest MP.
The SNP MP said she trusts her parliamentary colleagues but those from other parties make it difficult for her to “switch off”.
She added: “Given the unsociable hours that Westminster works as well, it feels like you’re spending a lot of your life there.
“In the run-up to the next election, I’ve realised, that will be almost 10 years that I’ll have been elected.
“So, a third of my life I’ve spent in Westminster, which gives me the ick.”
Black became popular early in her career after several clips of her speaking in parliament circulated on social media. She was praised for the way in which she got stuck into the Tories.
She successfully ran on a joint ticket with Stephen Flynn in the Westminster group's leadership election late last year. This came after longstanding group leader Ian Blackford stood down.
Labour Shadow Scotland Secretary Ian Murray said: “Mhari Black is the latest Nat to flee the sinking ship.
“The SNP has lost its way, and has lost touch with the Scottish people. They no longer stand up for Scotland but stand down for Scotland.
“They know the writing is on the wall - a Labour government is within grasp and they’d rather step aside than see Labour beat the Tories.”
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