ROME (Reuters) - The global economic crisis will hit jobs hard, with unemployment set to reach double digits in many developing and advanced countries, the Organization for Economic Cooperation and Development (OECD) said on Sunday.

"By the end of 2010 the unemployment rate could be approaching double digit figures in all G8 countries with the sole exception of Japan, as well as in the OECD area as a whole," the OECD forecast in a background paper to G8 labor and employment ministers gathering in Rome.

In new projections to be issued on Tuesday the OECD will forecast growth in the 30-nation bloc will contract by 4.2 percent this year, the Paris-based body's general secretary, Angel Gurria, told reporters on Friday.

The OECD had earlier predicted a 0.4 percent contraction, in November.

The paper released to reporters on Sunday projected that joblessness in the OECD area would increase in the three years to 2010 by more than it rose in the 10 years to the early 1980s, which included two oil shocks.

It forecast the area's economy would stage "a rather muted recovery" in the first half of 2010 if a series of conditions are fulfilled.

"Even this muted recovery rests on the assumption that tensions in financial markets dissipate toward the end of 2009, monetary and fiscal policies continue to be supportive and that growth will pick up in the non-OECD area," it said.

The OECD urged G20 leaders meeting in London this week to "intervene quickly and effectively to avoid the financial crisis becoming a full-blown social crisis with scarring effects on vulnerable workers and low-income households."

In a separate document prepared for the Rome G8 "social summit," which runs until Tuesday, the International Labour Organization warned that global unemployment could rise by 50 million this year, after an increase of 11 million in 2008.

John Evans, the leader of the trade unions in the OECD bloc, told reporters that workers' organizations should have formal representation at the London G20 to ensure that safeguarding employment is near the top of the agenda.

"Workers are paying the price of the crisis and anger is going to mount unless we get clear answers," he said.

The 30 nations which fund the OECD include the United States, Japan and the rich industrialized nations of Europe, while the narrower G8 is made up of the United States, Japan, Germany, Britain, France, Italy, Canada and Russia.