The gap in the average monthly salary between regular and irregular workers has widened by the biggest margin this year, according to latest data.

Statistics Korea on Tuesday said the average monthly wage among irregular workers between June and August stood at one-point-77 million won, up three-point-four percent on-year.

The average wage for regular workers during the same period jumped three-point-two percent on-year to three-point-34 million won. 

The salary gap between the two groups widened to one-point-57 million won, the largest since the agency began compiling related data in 2003.

Among irregular workers, a record 59-point-nine percent said they willingly took on irregular positions, up three-point-three percentage points from a year earlier.