Speaking in an interview with Dermot Murnaghan on Sky News, and introduced as "the most powerful advertising executive in the world", Sorrell said "this is not about independence, it is about separation".
He said: "Two of the biggest changes will be to the property industry in Scotland. Interest rates will rise, mortgages will be more difficult to come by and the financial services industry will be defenestrated as people move down south."
Sorrell also warned that the arguments in the 'Yes' campaign are political, not economic. He said: "What will happen is prices will rise, food prices, the food retailers have been quite clear about that. It’s not a conspiracy, they are just saying what will happen.
"Interest rates will rise, there will be considerable instability, investment will fall and the Scottish economy depends very heavily on government employment. Where is the money going to come from to continue to employ those people in government?"
WPP’s chief executive wondered, "how will Scotland try and position itself?"
He dismissed the possibility of Scotland being able to position itself as a sort of Singapore or a Uruguay, claiming its geographical and historical position will make it more of "an outlier".
He said: "Glasgow, Edinburgh will be cities that will be outliers, not at front and centre in global business thinking.
"London actually, ironically, will become even more competitive to Edinburgh or Glasgow as a centre for global corporations and I don't think in that competitive environment that a city state of Scotland will win out in competing for business."
If WPP does find itself operating in 111 countries, as opposed to 110, by the end of the week, the implications "are not good", warned the chief executive.
He noted: "The UK accounts for about 10 per cent of our revenues and our profits on a global basis. As I look at WPP in the future, what we will do is spend more investment money outside the UK in trying to develop our business beyond the UK borders with increasing intensity.
"The digital area in the UK will become more and more important, but certainly geographically the UK will be diminished and the pity about this is that we are turning in and on ourselves, Dermot and not growing the whole of the UK."