SEOUL -- Another former South Korean president faces a criminal investigation, as prosecutors gear up to look into Lee Myung-bak's alleged abuse of power during his five years in office from 2008 to 2013.

Seoul Mayor Park Won-soon on Tuesday filed a complaint with prosecutors, accusing Lee of abuse of power. Park said the former president approved plans by South Korea's intelligence agency to defame him and his family by spreading false rumors.

"The National Intelligence Service and groups influenced by the agency raised numerous questions about my son's military service," Park said in a radio interview with South Korean broadcaster CBS. "It turned out to be baseless, with 15 instances [of medical examinations], but they continued to attack cruelly by mobilizing people and posting comments on the internet."

Park's son was exempted from two years of compulsory military service in 2011 due to a herniated disk in his lower back. Instead, he served at a public institution.

Dirty tricks?

The investigation comes as a task force at the NIS investigates 15 cases, including Park's, in which the agency allegedly conducted unlawful operations against citizens. In August, an appeals court sentenced former NIS chief Won Sei-hoon to four years in prison for improperly swaying public opinion by posting hundreds of thousands of comments on the internet.

Former President Lee has not issued an official statement on Park's allegations, but his aides said the probe amounts to political retaliation. Rep. Choung Byoung-gug of the center-right Bareun Party said that such accusations will only create conflict and divide the country, saying "blood calls for blood," in an interview with CPBC radio.

In addition to Park, a number of actors, novelists and artists are also considering suing Lee for the spy agency's alleged surveillance. Actor Moon Sung-keun plans to file civil and criminal complaints against Lee in October, alleging that he approved the agency's plan to create a blacklist of actors who opposed him.

"As of Sept. 20, 5 p.m., 21 people are taking part in the 'MB NIS Blacklist' lawsuit case," said Moon on Twitter. The plaintiffs include novelist Lee Oe-soo and movie director Park Chan-wook.

Many of South Korea's former presidents have been the subject of criminal probes. In March, former President Park Geun-hye was arrested for allegedly taking tens of billions of won (tens of millions of dollars) in bribes from business leaders, including Samsung Electronics Vice Chairman Lee Jae-yong. Park's case is pending at a Seoul district court.