Transparency International's annual Corruption Perceptions Index shows Spain, Portugal, Italy and Greece with the lowest scores in Western Europe.
The index measures the perception of corruption in the public sector and not the financial sector, but Transparency's Europe director Anne Koch told The Associated Press said the results clearly indicate that people in the countries worst hit by the crisis perceive corruption to be widespread.
"It seems to me to be quite blatantly obvious that the lack of transparency in public finances in these four countries has been reflected in the figures," she said.
On a scale newly introduced for this year's report, where 0 is "highly corrupt" and 100 is "very clean," two-thirds of the 176 countries ranked scored below 50, which Transparency said indicates a widespread need for more openness in public institutions and more accountability for officials.
"Governments need to integrate anti-corruption actions into all public decision-making," said Transparency International head Huguette Labelle. "Priorities include better rules on lobbying and political financing, making public spending and contracting more transparent and making public bodies more accountable to people."
The survey, which was first conducted in 1995, draws on a variety of sources that capture perceptions of corruption, including World Bank and World Economic Forum assessments, the African Development Bank's governance ratings, and Transparency International's own Bribe Payers Survey.
Afghanistan, North Korea and Somalia were ranked the worst overall on this year's list, all tied with a rating of just 8. Denmark, Finland and New Zealand were thought of as least corrupt with scores of 90.
Canada scored 84, Germany 79 and Japan and Britain tied at 74. The United States was rated 73, giving it 19th place, and France scored 71.
At the bottom of western European nations, Greece scored a 36, Italy 42, Portugal 63 and Spain 65. All four countries are mired in recession, and both Portugal and Greece have received EU bailouts.
The Greek numbers, which put it in 94th place on the ranking, stand out in particular, Koch said. If the new 2012 methodology is applied to the 2011 results, Greece fell by 14 places.
"Greece, of course, at place 94 is the lowest state in the European Union," she said. "It's ranked lower than countries like Colombia, Benin and Zambia ... which gives you pause for thought."