In its latest survey, the body urged more stringent -- and speedier -- regulations for Switzerland's two biggest banks to protect the economy and taxpayers in times of financial crisis.
Credit Suisse and UBS "continue to pose large systemic risks," the OECD warned.
Lawmakers agreed a set of measures in September designed to make financial institutions better equipped to absorb losses in future, including a capital ratio of 19 percent and a leverage ratio of five percent. The legislation will not be fully implemented until 2019.
The OECD said the reforms would go a long way to reducing dangers but that the leverage ratio figure, which limits the amount of debt that can be used to finance the bank's assets, "is still modest in view of the risks involved."
"The need for substantial tightening of capital requirements is reinforced by the absence of an internationally co-ordinated resolution mechanism which could help avoid the rescue of a failing bank by the government," said the report.
"It is crucial that, at the least, the proposed capital requirements for the Big-2 are implemented in full. A stricter leverage ratio requirement should be introduced."
Swiss banking is dominated by Credit Suisse and UBS. The latter suffered major losses in the 2008 financial crisis and was the subject of a government rescue package including a capital injection of six billion francs ($6.4 billion).
While Swiss banks' direct exposure to the current euro debt problems is low, "Switzerland could be affected by global financial turbulence through the banking sector," OECD secretary general Angel Gurria said while presenting the report in Bern.
Swiss Economics Minister Johann Schneider-Amman told the conference that the recent legislation had been agreed as part of an "acceptable compromise" among lawmakers and that the schedule was fixed for its implementation.
"The important issue is that we came to a reasonable decision, we have got to follow it and we will achieve it at the latest by 2019," he said.
"In the meantime it is in the best interests of the two big guys concerned to make sure that they achieve their stability.
"If it is done earlier and more ambitiously," then nobody would blame them, said the minister, addressing media in English.
In its analysis of the Swiss economy in the same survey, the OECD said recovery from recession slowed in 2011 and forecast a period of stagnation in the near term, particularly in the manufacturing sector, due to decreased trade and the strong Swiss franc.
This is in line with the forecast of the Swiss government which predicts weak or negative growth at the start of 2012 but ending the year with 0.5 percent growth, compared with 0.8 percent growth in 2011.
"The economic stability of Switzerland has stood out in the context of economic and financial instability in the rest of the world," said Gurria, who attributed the country's "early, balanced" recovery from the financial crisis to its sound budgetary rules and labour market.
Switzerland, with its youth unemployment figure at 2.5 percent last year, represented a "dramatic exception" from other OECD countries where the figure is closer to 20 percent and in some cases 30 or 40 percent, Gurria said.