It will be very damaging for the stability of Europe if the United Kingdom leaves the European Union under "Brexit," a former president of the European Central Bank says.
"The main problem, of course, is that the UK is taking enormous risks, not only economically, financially, historically—I would said also in terms of its own flag," Jean-Claude Trichet told CNBC's "Closing Bell" on Friday. "If Scotland takes advantage of the situation to restart the process of getting out, you'd have to change the Union Jack."
The United Kingdom is set to hold an in-out referendum that will determine whether the country will stay or leave the European Union on June 23.
Trichet said he believes the UK will not exit the European Union because, "it's so clearly against the interest of the UK."
"The UK is profoundly welcomed in the European Union, and that, of course, makes all of us trust that the UK will stay."
The European Union would lose its second largest economy and up to $3 trillion in GDP, if Britain decided to part ways with the 28-nation economic bloc.
The former monetary policy official contends that the UK's security and defense would be threatened if it voted to leave the EU.
"It goes without saying that, from a financial standpoint, it would be a catastrophe for the UK to leave," Trichet said on Friday.
—CNBC's Fred Imbert contributed to this report.