An Edinburgh woman behind a ‘landmark’ legal challenge on biological sex has been told she “deserves” to die in a barrage of hate mail.

Marion Calder, a single mum from the city, set up campaign group, For Women Scotland, alongside Susan Smith and Trina Budge that has won a three-year battle at the Supreme Court after judges unanimously ruled the definition of a woman is based on biological sex.

Since their win in Supreme Court on Wednesday, April 16, they’ve been overwhelmed with death threats and online abuse, reports the Daily Record.

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In an interview with The Sunday Times, the 55-year-old said: “Sadly, it is almost inevitable that women who speak up for our rights will be threatened by angry men. It’s a tale as old as the hills.

“Ironically, this lot think they are on the side of ‘progress’, ‘kindness’ and ‘human rights’, but they have no issue using the most dehumanising, sexist abuse or threatening the most extreme violence.

“Thankfully, the nastiness is dwarfed by messages of love and support, many of which have brought us to tears.”

Messages sent to the organisation’s email address included: “You’re a group of disgusting murderers and deserve death.”

“God will rip you from your family one day and nobody will mourn you.”

Another read: “Your inhumanity makes me vomit.

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“You stupid women should feel deeply ashamed for being so stupid.”

Former financial adviser and mum-of-three Susan, 53, added: “It would never occur to us to send messages like this or to call our opponents ugly. But we get this every day.”

Marion, Susan and Caithness farmer Trina, 54, met on parenting website Mumsnet in 2018.

During their campaigning, Marion said trans activists were also continually throwing “insults” at them. She explained: “First they said we’re transphobes, then they called us homophobes, then it was bigots, now they say we’re pro-Trump. It’s all completely ridiculous.”

By 2020, the Scottish Government and then first minister Nicola Sturgeon were increasingly focused on passing the Gender Recognition Reform Bill, which would usher in self-ID, and lower the legal age when young people can transition to 16.

The bill was passed in 2022, but blocked the following year by then UK prime minister Rishi Sunak.

Susan, who underwent a single mastectomy after being diagnosed with breast cancer, gave a speech in the Scottish Parliament 10 days after her surgery.

She said: “Having gone through a mastectomy myself, which I needed to save my life, I am disgusted by people who celebrate giving mastectomies to healthy young women as a ‘gender-confirming’ surgery. I think it is genuinely wicked”.

FWS’s argument with the Scottish Government boiled down to whether the Equality Act 2010 says that a trans woman with a gender recognition certificate, which can be bought for £6, is the same as a female.

The Scottish government said it did. FWS disagreed. In February last year, the women were given permission to appeal to the Supreme Court after the Court of Session ruled against them.

Marion said: “It was a big gamble but we decided the appeal was worth it, because even if we lost, it would show that the law currently makes no sense”.

It ruled that, while the Gender Recognition Act 2004 protects trans people from discrimination, the Equality Act 2010 defines a woman as an adult female, not a man who wishes to identify as a woman, as the Scottish Government repeatedly insisted.

The decision resulted hundreds of people marching on the streets of Edinburgh at the weekend in protest of the ruling.

Despite their success, Marion, Susan and Trina say their work is “nowhere near done”, and will continue after they’ve had a “gigantic party”.