Income inequality is at record levels in the developing world and the United States and Israel are leading the pack.

According to a report from the Organisation for Economic Co-operation and Development (OECD), the U.S. and Israel have the worst inequality in the developed world, with the gap at its highest level in 30 years.

In the U.S., the richest 10 percent of the population earn 16.5 times the income of the poorest 10 percent. The richest 10 percent of Israelis earn 15 times that of the poorest.

Among all OECD member nations, the "richest 10 percent of the population earn 9.6 times the income of the poorest 10 percent," the report said.

Data from 2012 shows that among 18 OECD member nations, half of the total wealth was controlled by the top 10 percent of the population, while the next 50 percent hold nearly all of the second half, leaving the bottom 40 percent owning just 3 percent of the wealth, CNN reported.

The U.S. also has the widest wealth gap, with the top 5 percent of U.S. households owning almost 91 times the wealth of the average household.

Mark Pearson, author of the 330-page report, attributed the record level of inequality in the U.S. and Israel to comparatively low spending on social programs and benefits. He pointed to countries like France as doing better to redistribute wealth through taxes and benefits.

"Redistribution via taxes and transfers is a powerful instrument to contribute to more equality and more growth," the report said.

OECD said another contributing factor in the U.S. is a wider skill gap between the richest and poorest, which leads to lower quality and productivity in the workforce, with highly skilled people able to command significantly bigger salaries than lower skilled workers.

Doctors in the U.S., for example, are able to make much more money than they can in the United Kingdom and Germany, while low skilled laborers in the U.S. usually make less than they would in other countries, Pearson said, according to CNN.

OECD also said an increase in non-standard work, such as temporary work and self-employment, was responsible for the growing inequality. More than half of all new jobs created in OECD countries over the past decade fell into this category, and families that rely on non-standard employment are more likely to be poor, the report said.

Israel has a particular problem with encouraging women to enter the workforce, which can prevent poor families from getting ahead, Pearson said, noting that religious and cultural factors have kept many women out of the workforce.

"More women in work really does seem to have an effect on inequality," Pearson said, according to CNN. "It reduce[s] inequality."

OECD warned that the rising level of inequality not only affects individual nations, but hampers world economic growth as a whole.

"High and often growing inequality raises major economic concerns, not just for the low earners themselves, but for the wider health and sustainability of our economies. Lower income people have been prevented from realizing their human capital potential, which is bad for the economy as a whole," the report says. "Put simply: rising inequality is bad for long-term growth."