Youth unemployment across the world has climbed to a new high and is likely to climb fur

ther this year, a United Nations agency said Thursday, while warning of a “lost generation” as more young people give up the search for work.

The agency, the International Labor Organization, said in a report that of some 620 million young people ages 15 to 24 in the work force, about 81 million were unemployed at the end of 2009 — the highest level in two decades of record-keeping by the organization, which is based in Geneva.

The youth unemployment rate increased to 13 percent in 2009 from 11.9 percent in the last assessment in 2007.

“There’s never been an increase of this magnitude — both in terms of the rate and the level — since we’ve been tracking the data,” said Steven Kapsos, an economist with the organization. The agency forecast that the global youth unemployment rate would continue to increase through 2010, to 13.1 percent, as the effects of the economic downturn continue. It should then decline to 12.7 percent in 2011.

The agency’s 2010 report found that unemployment has hit young people harder than adults during the financial crisis, from which most economies are only just emerging, and that recovery of the job market for young men and women will lag behind that of adults. The impact of the crisis also has been felt in shorter hours and reduced wages for those who maintain salaried employment.

In some especially strained European countries, including Spain and Britain, many young people have become discouraged and given up the job hunt, it said. The trend will have “significant consequences for young people,” as more and more join the ranks of the already unemployed, it said. That has the potential to create a “ ‘lost generation’ comprised of young people who have dropped out of the labor market, having lost all hope of being able to work for a decent living.”

The report said that young people in developing economies are more vulnerable to precarious employment and poverty.

About 152 million young people, or a quarter of all the young workers in the world, are employed but remain in extreme poverty in households surviving on less than $1.25 a person a day in 2008, the report said.

“The number of young people stuck in working poverty grows, and the cycle of working poverty persists,” the agency’s director-general, Juan Somavia, said.

Young women still have more difficulty than young men in finding work, the report added. The female youth unemployment rate in 2009 stood at 13.2 percent, compared with the male rate of 12.9 percent. The gap of 0.3 percentage point was the same as in 2007.

The report studied the German, British, Spanish and Estonian labor markets and found that Germany had been most successful in bringing down long-term youth unemployment. In Spain and Britain, increases in unemployment were particularly pronounced for those with lower education levels.

Data from Eurostat, the European Union’s statistical agency, show Spain had a jobless rate of 40.5 percent in May for people under 25. That was the highest level among the 27 members of the European Union, far greater than the 9.4 percent in Germany in May and 19.7 percent in Britain in March.