The Scottish poverty relief charity The Dignity Project has said that a message on its Twitter account calling the Harry Potter author JK Rowling a "bitch" for making a £1m donation to the anti-Scottish independence campaign Better Together was the result of its account being hacked.

The Office of the Scottish Charity Regulator said in a statement that it was "making urgent inquiries" as a result of the tweet, posted on @DignityProject at just after 12 noon today.

It was widely reported today that Rowling had made a £1m donation to the Better Together campaign.

The tweet from the Dignity Project account says: "What a #bitch after we gave her shelter in our city when she was a single mum." It contains a link to a story on the website of The Guardian newspaper about the author’s donation.

What a #bitch after we gave her shelter in our city when she was a single mum. http://t.co/6hYglHV2sk — The Dignity Project (@DignityProject) June 11, 2014

In a statement posted on its website, the charity said: "The Dignity Project has had its Twitter account hacked. We are not responsible for any tweets that have been sent. As a charity we do not take any political stance and our opinion is that people are free to donate to whoever they choose. To the people who hacked our account – if helping African children to thrive and survive, including single mums, is a bad thing, that is their problem."

The Edinburgh-registered charity exists to relieve poverty and advance education for children in Africa, and to advance the Christian religion in the continent.

The OSCR said in a statement: "We are aware that a number of concerns have been raised today about a tweet from Scottish charity The Dignity Project. We are making urgent inquiries into the matter and will be seeking further information from the charity trustees."