South Korean parliamentary speaker Park Hee-tae announced his resignation on Monday for allegedly giving bribe to win the chairmanship of the ruling party in 2008.

Park is suspected of having offered cash envelops to fellow ruling party members in a vote-buying attempt before the party leadership contest, where he was elected head of the conservative Grand National Party, which was renamed as the Saenuri (New World) Party.

"I do not intend to make an excuse that (vote-buying) has long been common practice in political circles," Park told reporters after submitting his resignation to the parliament. "I am to blame for everything."

His two-year term was due to expire in May.

The announcement came after Kim Hyo-jae, the senior presidential secretary for political affairs who served as a secretary for Park, offered to step down last week over his alleged involvement in the scandal.

The scandal has been a blow to the ruling party as it struggles to recover from recent election defeats and reshape itself ahead of key polls this year.

Both Park and Kim are expected to be summoned soon by prosecutors for questioning.