President Yoon Suk-yeol voiced regret Wednesday after the main opposition party boycotted his budget speech, saying the party has left a bad precedent that could weaken public confidence in the National Assembly.

Yoon delivered a budget speech in a half-empty National Assembly hall Tuesday after the main opposition Democratic Party decided to boycott the session in protest over the prosecution's recent raid of its headquarters and other actions it described as suppression of the opposition.

"It's a shame that something that has established itself as a custom in the history of our constitutional government, regardless of the political situation, over the past 30 or so years, starting from the days of President Roh Tae-woo, collapsed as of yesterday," Yoon told reporters as he arrived for work, referring to presidents delivering budget speeches before a full parliamentary session.

"From now on, it's possible members of the National Assembly will every now and then not attend a president's budget speech depending on the political situation, and wouldn't that ultimately further weaken the people's confidence not only in grand unity but also in the National Assembly?" he added.

Yoon said he believes there is room for reflection on whether such action is desirable for the National Assembly and that good practices should be maintained regardless of the circumstances.

Yoon's speech came a day after the prosecution raided the Democratic Party headquarters to seize evidence in connection with a corruption scandal that led to the arrest of a key confidant of Democratic Party leader Lee Jae-myung over the weekend.

Lee has called for an independent counsel investigation into the scandal amid fears the prosecution could be zeroing in on him.

Yoon declined to comment when asked to respond to Lee's request.

"Have a good day," he said. "Many people have already stated their positions on that." (Yonhap)