Justice Minister Park Beom-kye on Wednesday exercised his investigation command authority over a case involving Han Myeong-sook, a former prime minister convicted of taking bribes.

The move came as the statute of limitations is set to expire on Monday in an alleged perjury case, in which prosecutors are suspected of forcing inmates who spent time in prison together with the man who bribed Han to make false testimonies against her in 2011.

Earlier this month, the Supreme Prosecutors Office (SPO) dropped charges against two witnesses and investigators who are allegedly implicated in the allegations.

In a briefing, the ministry said Park ordered the SPO to conduct a last-minute probe to see if there was any "unreasonable decision making" by investigators in dismissing the charges and to produce an investigation result on the issue by Monday.

The justice minister's invocation of his authority marked the fourth such action in South Korean history.

Han, who served as prime minister from 2006-2007, was imprisoned in 2015 after the Supreme Court convicted her of accepting about 900 million won ($793,301) in illegal political funds from Han Man-ho, the late CEO of a local construction company. The two are not related.

The former prime minister was released from prison in August 2017 after serving her sentence.

She has long claimed innocence, arguing that she never accepted the money and that the charges against her were fabricated as part of political revenge by a conservative government against the former liberal administration of late President Roh Moo-hyun. Her supporters, including former Justice Minister Choo Mi-ae, have also long claimed that Han was convicted of trumped-up charges.

Her case grabbed public attention in May last year when the ministry received a complaint from a prison inmate who claimed that prosecutors pressed the late executive's fellow inmates to testify against the former prime minister. (Yonhap)