There were around 12.53 million nonregular workers in Japan in 2010, of whom 1.49 million served as breadwinners of households with less than ¥3 million in annual income, the labor ministry said Friday in a white paper.

Around 570,000 men and some 920,000 women were the breadwinners in such households, the welfare ministry said.

Based on the findings, the ministry stressed the need to stabilize employment and improve labor conditions by giving these workers chances to bolster their skills.

To help them achieve permanent status, the ministry called for using a system that allows them to be employed on a stable basis but under narrow labor conditions, with duties and work locations restricted.

Less than 40 percent of companies are using such a system, the white paper said.

"The system will enable workers to balance their work and life," it said.

Low income households include singles earning under ¥2 million a year and under ¥3 million for those of two or more people.