Harry Potter author JK Rowling has accused the movement to Leave the EU of in 'some instances' being directed by 'racists'.

Rowling's comments on Thursday's referendum were made in a 1723-word essay published on the author's website.

The author also said it was "nonsensical" to suggest "racists and bigots... aren't flocking" to Leave ahead of the vote on the UK's membership of the supranational body.

She wrote: "It is dishonourable to suggest, as many have, that Leavers are all racists and bigots: they aren't and it is shameful to suggest that they are.

"Nevertheless, it is equally nonsensical to pretend that racists and bigots aren't flocking to the 'Leave' cause, or that they aren't, in some instances, directing it. For some of us, that fact alone is enough to give us pause."

The author, who lives and works in Edinburgh, said a recent poster unveiled by Ukip leader Nigel Farage was "an almost exact duplicate" of Nazi propaganda.

She continued: "The picture of Nigel Farage standing in front of a poster showing a winding line of Syrian refugees captioned 'Breaking Point' is, as countless people have already pointed out, an almost exact duplicate of propaganda used by the Nazis."

Rowling was also scathing of the referendum campaign more broadly. She described it as "one of the most divisive and bitter political campaigns ever waged" in the United Kingdom.

Leave.EU - the pro-Brexit organisation backed by Farage and Ukip donor Aaron Banks - hit back at Rowling's comments calling them "unsubstantiated".

A Leave.EU spokesman said: "Ms Rowling was absolutely right to say that it is 'dishonourable' and 'shameful' to suggest that all Leavers are racists and bigots. She might have gone further, and said that it is 'dishonourable' and 'shameful' to try and shut down people with legitimate concerns about immigration by accusing them of racism and bigotry for expressing them.

"It would have been better for everyone if she had left it at that, rather than indulging in unsubstantiated claims about extremists 'flocking' to the Leave banner and drawing comparisons between Leave campaigners and the Nazis."

The spokesman then went on to accuse the Remain side of the referendum debate of containing "prominent members and supporters of the IRA".

This is not Rowling's first intervention into a referendum campaign.

During the 2014 referendum on Scottish independence Rowling penned a similar essay outlining her support for the No campaign.

The author went on to donate £1m to Better Together.

Voters across the UK will go to the polls on Thursday to decide if Britain should vote to Leave or Remain inside the European Union.