Oswald Gruebel, who led both of Switzerland's two biggest banks during his career, criticised negative interest rates and argued they'd lead to a further decline of the country's financial sector.

"Negative interest rates are crazy. That means money is not worth anything any more," Gruebel said in an interview with Swiss newspaper NZZ am Sonntag. "

Former UBS and Credit Suisse chief Oswald Gruebel. Credit:Tamara Voninski

As long as we have negative interest rates, the financial industry will continue to shrink."

Gruebel served as Credit Suisse CEO from 2004 to 2007 and as UBS Group AG's top executive from 2009 to 2011.