The Organization for Economic Cooperation and Development said as many as 34.8 million could be out of work by the end of next year, the Financial Times reported.
As the world's economies began the current slowdown from a position of relative strength, however, the unemployment rate will be only slightly worse than in 1995 and 2005, OECD General Secretary Angel Gurria said.
"Labor markets have shown significant improvements over the past decade. The average unemployment rate dropped to 5.6 percent in the OECD area in 2007, the lowest rate since 1980," OECD said.
OECD said the unemployment rate would remain unchanged in Japan and Korea.
Unemployment in the United States, now at 5.5 percent, is expected to rise to 6.1 percent, the report said.
In Europe, unemployment was expected to remain "essentially unchanged" for the next two years with the biggest rises in Iceland, Ireland, Spain and Turkey, the report said.
In the Czech Republic, Poland and the Slovak Republic, unemployment rates are expected to fall, OECD said.