The writer of the popular Matthew Shardlake books, who has been vocal about his opposition to the SNP in the past and has donated to the Better Together campaign, said he senses "growing polarisation within Scotland" because "nationalism is always visceral and destructive" and added: "this often seems less a debate than a rancorous argument, which I fear will leave scars."
However the writer, who has set novels in Civil War-era Madrid as well during an alternative history of the Second World War, said that while the Yes campaign, thus far, has been well organised and "clever", the No campaign had "misfired" on certain issues.
Sansom, born and educated in Edinburgh, made headlines in 2012 when he included a "historical note" in his latest novel, Dominion, in which he said that beneath the "empty populist bonhomie of Alex Salmond, the prospective break-up of Britain is already creating a new culture of hostility and bitterness on both sides of the Border".
More than a year later, the Sussex-based writer who has sold more than two million books during his career, said: "Happily, I was wrong there; south of the border opinion polls show most agreeing with David Bowie's sentiment: 'Please don't go.'"
The referendum campaign has shown a marked and vocal support for Independence from many writers, artists and figures in the cultural sphere, including the National Collective group of young artists.
When asked why more cultural figures have not been outspoken in support of the No campaign, as he has been, he said: "Sadly, the cold dead hand of romantic nationalism still seems to attract some involved in 'culture.'
"I have heard the view that those based in England, like me, are not entitled to a voice.
"But that is to concede the Nationalist frame of reference, and accept a narrowing of the debate; a self-censorship.
"I'm not entitled to a vote, of course, but I believe everyone is entitled to a view, on this issue as on anything else - and this affects everyone in Europe.
"Then I've heard the argument that cultural figures are not entitled to a special voice...quite right, but again, everyone is entitled to a voice, not just the politicians."
Sansom said that the Yes campaign has been slick but added: "Like all populist parties, the SNP have the advantage that they can bend to the wind, and evade hard questions with easy words; this is what they have done; their empty slogans of 'newness' remind me of Tony Blair's campaigns.
"They cleverly themselves as the party of change, and therefore positivity; calling the 'No' campaign Project Fear.
"And there is much to fear, because the economics is crazy, and national identity is such a lunatic basis for politics."
He went on to say that the Better Together campaign had "misfired", including the involvement of George Osborne in the currency debate, and the "clumsy" intervention of European Commission President Jose Manuel Barroso, which "put people's backs up."
However the author added: "The argument now is increasingly about the 'heart.'
"I think the 'no' side might usefully put more stress on how national identity politics is not new in Europe but tired, old and failed; and what Yes Scotland portray as a positive message is actually a negative one, nationalism having delivered nothing but trouble in Europe."
Sansom said he believes the referendum result will be close.
He added: "The No camp have won the 'head' argument, and have been honest and realistic in pointing out the dangers and uncertainties, but superficially, 'No' is always a harder answer than yes.'
"The 'No' campaign cannot present a 'united' picture.
"Politics should ideally be about alternative answers to questions about political economy and not the easy fudge of national identity politics."