President Lee Myung-bak's former senior secretary appeared before prosecutors for questioning early Wednesday for his suspected involvement in the allegations that former National Assembly Speaker Park Hee-tae bribed fellow lawmakers to win the ruling party's chairman post in 2008.

Kim Hyo-jae, who worked as Lee's chief political-affairs secretary, arrived at the central prosecutors' office in southern Seoul at 9:21 a.m. He resigned from the post earlier this month amid rising suspicions.

"I am sorry for having caused concerns to the public.... I will sincerely respond to prosecutors' questions," Kim told reporters as he entered the office.

Kim is suspected to have played a key role in Park's alleged vote-buying during the 2008 chairman election of the ruling Grand National Party, now renamed the Saenuri Party.

Park allegedly distributed envelopes containing bundles of cash to fellow lawmakers and other party members right before the party convention, possibly using illegal political funds provided by a private company.

Park had strongly denied the allegations since they emerged in early January before stepping down as a parliamentary speaker last week with a pledge to take responsibility for the scandal.

Kim was the emergency monitoring chief for Park's election camp during the allegedly bribery-ridden party convention.

Kim's former aide has been pinpointed as one who delivered bribe money to some ruling party lawmakers.

Park, the GNP chairman between 2008-09, dropped his party affiliation and became parliamentary speaker in 2010. (Yonhap News)