Last week's U.K. Treasury report and the recent IMF report are the latest in a long line of predictions suggesting doom and gloom if the United Kingdom leaves the European Union. Are they right?

Economists are far more split on the consequences of a U.K. exit than the conventional view suggests. While a number of global investment banks have given dire warnings of negative fallout, just as many reports from respected economists or independent City firms — including Capital Economics, Toscafund and Peel Hunt — have concluded that the "Brexit" threat is overblown.

Even the recent report by PwC predicts financial services would continue to grow strongly outside the EU, after some short-term uncertainty.