South Korea's Parliamentary Speaker Park Hee-tae will announce his resignation on Thursday, holding himself responsible for the widening investigation into allegations that he bribed fellow lawmakers during campaigns for a 2008 leadership election of the ruling party.

The 74-year-old Park has been dogged by suspicions that he distributed cash-stuffed envelopes to fellow ruling party lawmakers and district party council members to muster votes for his 2008 bid to become the head of the then Grand National Party, which recently changed its name to the Saenuri Party.

Park dropped his party affiliation to become the parliamentary speaker in 2010.