Lawmakers were questioning leaders of big businesses in a rare TV hearing, as part of a huge corruption inquiry.
Eight firms admit donating funds linked to President Park Geun-hye, but deny seeking favours.
Parliament is due to vote on Friday on Ms Park's impeachment over the scandal.
Massive protests have been held in recent weeks demanding her resignation.
The executives are being questioned by a cross-party committee of lawmakers. The panel has no power to punish but its chairman has said the hearing is a place for apology.