The consequences of a British vote to leave the European Union (EU) would parallel the collapse of U.S. investment bank Lehman Brothers, an event that triggered the global financial crisis, warned Alexander Stubb, Finland's former Prime Minister.
"There's not one economist in the world who would see a Brexit as a good thing to either the United Kingdom (U.K.), EU or global economy....I would say if Britain were to vote out, we would see far-reaching market turbulence," he told CNBC's Capital Connection on Thursday.
Stubb, also Finland's outgoing finance minister, believed the U.K. was an instrumental part of the EU despite its reputation as a "a reluctant bride" ever since it joined the European Economic Community in 1973, referring to the U.K.'s long history of separatist tendencies.
A remain vote would not only strengthen the marriage, the U.K.'s status as a former great empire can help bring more clout to a recovering Europe, he added.
"If the U.K. decides to stay, that will also give a much stronger agenda for economic reform [in Europe]. If we cut red tape and liberalize the internal market for services, goods, capital and people, then all of Europe will be better off."
Economics aside, the EU's political fate is also at stake.
A Brexit could result in a domino effect across Europe, motivating countries including Italy and France to hold similar referendums. On Sunday, Luxembourg Foreign Minister Jean Asselborn told German newspaper Tagesspiegel am Sonntag that Eastern Europe was particularly at risk.
But Stubb insisted that wouldn't be the case for his home country.
"Finland is in the EU for economic and political reasons. We're not members of NATO so part of our security is the EU."