THE online abuse directed at Harry Potter author JK Rowling in the wake of her donation to the pro-UK campaign has reignited criticism over attacks by so-called "cybernats" - but one analysis of responses to news stories about independence has found more comments containing personal attacks on Alex Salmond than on David Cameron.

More than two-thirds - 67% - of responses to independence stories on the BBC website's UK pages which mentioned the SNP leader were negative, compared to 57% for the Prime Minister.

However, researchers warned both sides can be negative and it is difficult to gain a true picture of what is going on in social media due to, for instance, being unable to tell when comments are made in a bid to "hijack" the other side's campaign.

An apology was posted yesterday on the website of an Edinburgh-based charity being investigated by regulators for posting a tweet calling JK Rowling a "bitch".

The disclaimer on the website of the Dignity Project, which works in Africa, said it apologised for any offence caused by "having its Facebook account hacked, which was in turn linked to its Twitter account".

Dr Mark Shephard, a senior lecturer in government and public policy at Strathclyde University, cautioned that results relating to Salmond and Cameron were likely to be skewed by more comments coming from the far bigger number of residents in England.

But he added: "Both sides can be negative and politicians attract negativity, which is fine if it is about their work performance. But it is not nice and to be avoided if it is just a personal attack, in which a minority on both sides indulge."

Dr Shephard said it was difficult to assess social media on the independence debate as so much data was coming out on a "minute-by-minute" basis.

"Someone could present a study based on hashtags from the No side or hashtags from the Yes side and it will be a completely different picture," he said. "Unless we do an analysis of absolutely everything, it's going to be very difficult to say definitely which side is worse than the other."

He added: "No one side can claim moral high ground."

Shephard said it was also impossible to filter out comments made in parody or which may be from people purporting to be on one side but who are in fact trying to "hijack" the opposition's campaign.

He added: "I don't think people are saying online what they would have not said in their front rooms in the old days, it is just that now a growing number of people open that front room conversation up to others. What this is showing is there is a need for more education with regards to civility and etiquette."

The "armchair assassins" who targeted JK Rowling after she announced a donation of £1million to the Better Together campaign led to lists being circulated online of the worst tweets from what were dubbed "Scottish nationalists".

While some did sport Yes "Twibbons" on their profile and had previous references to the independence debate, the list also included tweets from those who will not have a vote in the referendum. For example, one which read "JK Rowling what a horrible c**t #free Scotland" was posted by Stephen Cooney, whose profile states he is from Dundalk, Co Louth.

The Office of the Scottish Charity Regulator has launched an investigation following a tweet posted by the Dignity Project referring to JK Rowling which said: "What a #bitch after we gave her shelter in our city when she was a single mum." It was still showing on the charity's Twitter feed last night.

The charity had initially posted a disclaimer which stated: "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 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."

Yesterday, the statement was updated to read: "The Dignity Project would like to apologise for any offence caused due to having it's [SIC] Facebook account hacked which was in turn linked to it's [SIC] Twitter account.

"The views expressed apparantly [SIC] in the message are not the views of the charity. The charity it's self [SIC] is not political and tries to take a non-biased view. Sincerely apologies. The Dignity Project."

The Dignity Project failed to respond to Sunday Herald requests for an interview.

Stephen Reicher, professor of psychology at St Andrews University, said the debate was becoming increasingly polarised online, with the sense of a "devious enemy" replacing honest debate.

He added: "I think a lot of the trolling is because people are not thinking of others as individuals, so they have less empathy about their feelings and how they will react.

"They just think of them as the enemy in exactly the same way as during a war: it is far easier to drop a bomb that kills 100 people than to shoot one person you can actually see."