The leader of the House of Commons claimed people north of the border had been portrayed by the party as “perpetually beaten and self-pitying” as part of a narrative blaming England for any troubles.
She said the narrative was fueled by “exaggeration, hysteria and hate” and described the SNP as “bile driven”.
Ms Mordaunt, who faced Rishi Sunak and Liz Truss in last year’s Conservative leadership competition, made her comments after visiting Scotland while speaking at the Edinburgh Festival Fringe on Sunday.
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On Thursday, she wrote in the Daily Express that the fresh start promised by the SNP in 2007 has proved “old as mountain” and people have said they are victims.
She said: “They promised a new way of thinking – a new party with a shiny brand that delivers results efficiently. A party of the people, for the people. Good people trusted in it.
“They were greatly disappointed.”
She said people in the rest of the UK have been urged to forget their family and said they are “the nation of the eternally beaten and self-pitying”.
Ms Mordaunt wrote: “Eventually you’re shaping it into a shiny new brand, updated for the modern age, and integrating it into social media. Then feed it hyperbole, hysteria and hatred. And then you look for someone to blame.
“The narration is modern but ancient. They were held down and held back by the old enemy, England and the English. They stole everything, the resources, the money, even your future.”
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However, she claimed that “the big lie of the SNP has been exposed” and the tide is turning against the party.
She said her visit to Scotland made her feel there was hope for the future and “personal and collective responsibility”.
She said, “There is hope and ambition from people and communities who want to do so much for themselves and for others.”