The SNP’s deputy Westminster leader Mhairi Black has said she will step down at the next general election, citing the “toxic” environment at Westminster as the reason for her departure.

Speaking to The News Agents podcast, the Paisley and Renfrewshire South MP said Westminster is “one of the most unhealthy workplaces that you could ever be in”.

She was first elected in 2015, when a surge in support for the SNP saw the party win almost every seat in Scotland. At that point she was the “baby of the House” – the youngest MP.

Scottish National Party Conference 2017
Ms Black said Westminster has left her feeling ‘tired’ (Jane Barlow/PA)

She told Emily Maitlis: “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.

“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, the MP was highly critical of the environment at Westminster.

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.”

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.”

In a statement released later on social media, Ms Black said she had decided some time ago not to seek re-election.

She said she had reassessed her “personal priorities” and wanted to spend more time with her loved ones.

Former SNP leader Nicola Sturgeon paid tribute to Ms Black, tweeting: “Both gutted by and entirely understanding of this. Her reasons resonate.

“But what a loss of a unique talent, not just to the SNP but to politics generally. I only hope it’s temporary.”

SNP Westminster leader Stephen Flynn simply tweeted that Ms Black is “in a class of her own”.

First Minister and SNP leader Humza Yousaf highlighted Ms Black’s impact on politics, saying: “She has been a trailblazer – a passionate supporter of independence, equality, social justice, and simply of trying to make life better for her constituents and the wider Scottish public.

“She has also served as a role model for young people, especially women, with an interest or a desire to get involved in politics.

“I know that Mhairi has been critical of the toxic, hostile environment of Westminster, which serves as an important wake-up call to those who are determined to safeguard our democracy.”

Scottish Parliamentary Elections 2021
Craig Hoy said there are ‘bitter’ feuds ongoing within the SNP (Fraser Bremner)

The Scottish Conservatives said Ms Black’s decision pointed to “failing leadership” from Mr Yousaf and Mr Flynn.

MSP Craig Hoy said: “As much as the depute leader tries to blame Westminster, in typical SNP fashion, the public won’t be fooled.

“Mhairi Black knows chaos is engulfing her party, which is why they are fighting like Nats in a sack.

“It speaks volumes about how bitter those feuds have become that Mhairi Black has thrown in the towel, just a few months after agreeing to become deputy leader, and decided not to fight another election despite not yet turning 30.”