TI's Corruption Perceptions Index 2012 ranked Denmark, Finland and New Zealand as the least corrupt nations, scoring 90 on a 100-point scale.
Two-thirds of the 176 countries ranked scored 50 or less, TI said.
TI said 75 percent of Europeans "consider corruption a growing problem in their societies."
In the eurozone, the 17 countries that share the euro as currency, Greece was ranked as the most corrupt, coming in at 94th followed by Bulgaria and Italy. The United Kingdom was 17th while France was 22nd and Germany was 13th. Elsewhere in Europe, Russia ranked 133rd, Ukraine, 144th, and Poland, 41st.
The United States ranked 19th, Canada 9th and Mexico 105th.
Venezuela was seen as the most corrupt South American nation at 165th while Chile and Uruguay were seen as the least corrupt at 20th.
In Asia, China ranked 80th and Japan tied with Britain at 17th. Iraq was 169th.
The least corrupt African country was seen as Botswana at 30th.
Australia ranked seventh.
"A growing outcry over corrupt governments forced several leaders from office last year, but as the dust has cleared it has become apparent that the levels of bribery, abuse of power and secret dealings are still very high in many countries," TI Chairman Huguette Labelle said in a statement.