Speaking to the press before he departs for Bahrain, Lee warned that the investigations would divide the public and stymie efforts for national security and economic growth.
"I am one of the people with a bit of expectation for the new government, but while watching the campaign to eliminate 'accumulated ills,' I have started to have suspicions about whether they really are reforms, or an expression of pent-up emotions or political reprisal," said Lee who ruled the country from 2008-2013.
"Such an act would not only divide public opinion, but also be unhelpful for our security at a crucial juncture and for South Korea's economy when it has to take advantage of the global economic recovery," he added.
Lee also stressed that the probes into the military and intelligence organizations would undermine national defense.
The National Intelligence Service and the military intelligence and cyberwarfare commands are under probe over suspicions that they mobilized operatives to post online comments in support of the former government, in violation of their obligation to maintain political neutrality.
The probes come as the liberal Moon Jae-in government conducts sweeping reforms under the name of "eliminating accumulated ills." But conservatives have dismissed the endeavors as "political retribution." BY THE YONHAP.
Lee embarked on a four-day visit to the Middle East country to deliver a lecture on South Korea's economic rise at the request of the Manama government. But the trip was overshadowed by public calls to bar him from leaving the country pending the investigations. As of Sunday morning, some 70,000 people filed petitions online for a travel ban.
On Saturday, former Defense Minister Kim Kwan-jin was arrested over his possible link to the cyberwarfare command's online activities allegedly aimed at swaying public opinion in favor of Lee's conservative government.
Kim's arrest has triggered calls for Lee to face justice as speculation persisted that the ex-commander-in-chief might also be involved in the political maneuvering scheme, either directly or indirectly.
The presidential office rebutted his criticism, saying that the current campaign is aimed at changing the structure of unfair privileges.
"During a meeting with the leaders of four opposition parties on Sept. 27, President Moon Jae-in said the elimination of accumulated ills has nothing to do with punishing and holding accountable certain persons, but it is about changing the structure of unfair privileges itself," presidential spokesman Park Soo-hyun said in a statement
In a Facebook post in September, Lee chafed at the campaign to redress alleged wrongdoings of past governments, saying that it would not only compromise national interests, but also end in failure.