Speaking at the Swiss bank's European Conference in London, Ermotti stressed that more was needed to address the region's economic issues.
"I think the ECB took a very pragmatic and realistic approach to the situation in Europe, strongly addressing this through the cut in rates. And I do think probably more is necessary to stimulate the economy," he said.
"I don't think this issue is only an issue for the ECB to handle. I do really think policymakers need to go through and address structural reforms in Europe... it's not just the ECB that can fix all the problems of Europe."
In a move that surprised many in the markets, the ECB cut its main interest rate to 0.25 percent from 0.50 percent on Thursday following surprisingly low inflation data that sparked concerns that the 17-country euro zone was heading for a period of deflation.
The data were followed by more underwhelming economic news - growth in euro zone business activity has slowed and retail sales fell more than expected - raising concerns about the region's recovery, and putting pressure on the ECB to act.
Ermotti also commented on the Swiss bank's increased provisions for litigation. UBS' third-quarter results included charges for provisions of 586 million Swiss francs ($636 million) for litigation, regulatory and similar matters.
(Read more: UBS profit beats but hurt by new capital demands )
"Investors are very concerned about the unpredictability of what's coming out, and they're asking what's going on," Ermotti said. "We have been spending a lot of time explaining what happened and reassuring them that those measures are temporary and we will be able to phase them out over time."
He added: "It looks to me like there is a long way to go."
The global banking sector was hammered by its role in the 2008 financial crisis and the rigging of the key bank rate Libor. The sector is now preparing to take another battering following the launch of investigations into the $3.4 trillion foreign exchange market by regulators both in the U.K. and the U.S.
(Read more: Banks brace for billion-dollar forex probe )
At the end of October, UBS joined other banks in confirming it was cooperating with investigators looking at the forex market.
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