JK Rowling has hit out at Scots who insist their nationalism “is nothing like the other, nasty kinds, in the face of considerable evidence to the contrary”.

The Harry Potter author lashed out on social media, insisting she had a “bulging folder of xenophobic and anglophobic screenshots” on her laptop.

But her outburst attracted a string of rebuttals, with SNP strategist Ross Colquhoun writing: “I’m not convinced finding a few tweets that confirm your blatant prejudice is justification for portraying pro-independence people as racists.”

Ms Rowling came out against independence in 2014, and previously compared a fringe of nationalists to Death Eaters – supporters of the evil Lord Voldemort in the Harry Potter books, who obsess over pure bloodlines.

Her remarks came after she took issue with a quote in the pro-independence newspaper The National by columnist Lesley Riddoch, who wrote: “Setting the English up as our automatic enemy doesn’t help us walk away from the Union mindset or its relentless pecking order.

“And yet like a packet of Crunchy Nut Cornflakes scoffed with cold milk late at night – it’s almost irresistible.”

The best-selling author dubbed Ms Riddoch’s comments “Crunchy Nut Nationalism”, adding: “Warning: may contain traces of bigotry.”

Read as a whole, Ms Riddoch’s article argues against “nasty or noisy gloating” from Scottish football fans towards the English during the World Cup.

Responding to a user who asked why she thought “Scottish nationalists are xenophobic, racist or anti-English", Ms Rowling then launched a series of tweets attacking nationalist rhetoric.

She shared a number of screenshots, including one from an account voicing support for controversial "ethnic nationalist" fringe group Siol nan Gaidheal, whose banners were spotted at recent marches.

She wrote: “When blood and soil ethno-nationalists are marching with your supposedly 'civic' marches, your nationalism doesn't look too different to any other country's.”

Another tweet she highlighted referred to the “rootless offspring of an immigrant”, accusing said person of wanting to “further dilute the genetic heritage of his host nation to make himself feel more comfortable”.

Ms Rowling wrote: “Nor does this kind of talk, from a self-proclaimed Scottish nationalist, quite square with the proud boast that 'our' nationalism is purer and better.”

She added: “Happy to take your word for it that such people aren't representative of the entire movement.

“Happy to accept that the bulging folder of xenophobic and anglophobic screenshots I have on my laptop aren't the whole story.

“But some of us are getting mighty tired of Scottish nationalist insistence that their nationalism is nothing like the other, nasty kinds, in the face of considerable evidence to the contrary.”

All of the Twitter accounts referenced by Ms Rowling were anonymous, while two had very few followers.

The SNP declined to comment.

But Scottish Tory MSP Annie Wells said there were “repeated examples of aggression and nastiness online and in person, together with a deluded attitude that Scottish nationalism is somehow different to other forms”.