Author JK Rowling has stated her support for a No vote in the Scottish independence referendum with a £1 million donation to Better Together and a blog detailing the "serious risks" of independence.

The Harry Potter author, who lives in Edinburgh, has written about her views on her website, highlighting her concerns about the economy and medical research.

Her donation is by far the biggest yet for the pro-union campaign, while Yes Scotland has benefited from £2.5 million from Colin and Chris Weir, who won £161 million in the EuroMillions lottery in 2011.

Writing in her blog, Rowling said that, while she is "no fan of the current Westminster Government", she has concerns about the economic risks of independence.

"My hesitance at embracing independence has nothing to do with lack of belief in Scotland's remarkable people or its achievements," she wrote.

"The simple truth is that Scotland is subject to the same 21st century pressures as the rest of the world.

"It must compete in the same global markets, defend itself from the same threats and navigate what still feels like a fragile economic recovery.

"The more I listen to the Yes campaign, the more I worry about its minimisation and even denial of risks."

The author, who was born in the West Country, but has lived in Scotland for 21 years, said there is a "fringe of nationalists who like to demonise anyone who is not blindly and unquestionably pro-independence".

"I suspect, notwithstanding the fact that I've lived in Scotland for 21 years and plan to remain here for the rest of my life, that they might judge me 'insufficiently Scottish' to have a valid view," she said.

Referring to characters from her Harry Potter books, she added: "When people try to make this debate about the purity of your lineage, things start getting a little Death Eaterish for my taste."

Criticism of the author quickly flooded in on Twitter, with one tweet from Edinburgh-based charity the Dignity Project reading: "What a #bitch after we gave her shelter in our city when she was a single mum."

Shadow Scottish Secretary Margaret Curran welcomed Ms Rowling's stance on independence and criticised the "vile abuse".

Ms Curran said: "I think it's really one of the most disturbing elements of this campaign that people are subjected to such abuse online. Particularly when we see voices from beyond the political world speaking and they are subjected to vile abuse.

"This has to stop. It's time to let people speak their minds freely without any fear of retribution."

The Prime Minister's spokesman also welcomed the support from the author and criticised online comments.

Speaking at a regular Westminster briefing, David Cameron's official spokesman said: "There is never any place for abusive behaviour in whatever sphere of life."

A spokesman for Yes Scotland said: "While we may disagree with her views, we of course completely respect JK Rowling and her right to express her opinion on the referendum and donate to the No campaign."

The author made her support for Better Together public earlier this year when she attended the campaign's fundraising night with comedian Eddie Izzard in Edinburgh.

Ms Rowling previously donated £10 million to set up a clinic at Edinburgh University to research treatments for multiple sclerosis, the degenerative disease that killed her mother, and she said her fears for the economy under independence extended to Scottish medical research.

"Having put a large amount of money into multiple sclerosis research here, I was worried to see an open letter from all five of Scotland's medical schools expressing 'grave concerns' that independence could jeopardise what is currently Scotland's world-class performance in this area," she wrote.

She concluded: "If the majority of people in Scotland want independence, I truly hope that it is a resounding success.

"Whatever the outcome of the referendum on September 18, it will be a historic moment for Scotland.

"I just hope with all my heart that we never have cause to look back and feel that we made a historically bad mistake."

A statement later posted on the Dignity Project website said its Twitter account had been hacked.

"We are not responsible for any tweets that have been sent," the statement said.

"As a charity we do not take any political stance and our opinion is people are free to donate to whoever they choose."