The prosecution said on Sunday it plans to question three opposition party officials as part of a probe into a fraudulent allegation about President Moon Jae-in's son during the election earlier this year.

A member of the minor People's Party named Lee You-mi was arrested Thursday for spreading misinformation that Moon used his influence to help his son, Joon-yong, get a job at a public agency in late 2006. 

Prosecutors investigating the case said they have summoned three campaign officials to appear for questioning Monday. They include Lee Jun-seo, a former member of the party's leadership panel.

Lee You-mi confessed to creating the anonymous tip-off and handing it over to Lee Jun-seo. The prosecution has barred Lee Jun-seo from overseas travel on suspicions that he is behind the smearing scheme.

Lee You-mi reportedly stated she didn't act alone. The People's Party and Lee Jun-seo have insisted that they had no knowledge of the scheme.

The intensifying scrutiny is putting pressure on the party's former leader and then Moon's rival Ahn Cheol-soo to clarify his stance. He is yet to make any official statement. (Yonhap)