Tensions between the ruling and main opposition parties are intensifying, as prosecutors investigations close in on Democratic Party Chairman Rep. Lee Jae-myung.

After a previous failure to raid the party’s Institute for Democracy think tank in Yeouido, Seoul, the prosecution again raided the institute Monday morning as part of its investigation into its Vice President Kim Yong, a close aide to Lee Jae-myung.

The Democratic Party immediately criticized the move and postponed the ongoing parliamentary audit in protest.

Party spokesperson Park Seong-joon said, "At about 8:45 a.m., 17 people including prosecutors entered the eighth floor of the Democratic Party building by surprise.”

"(Prosecutors) did not notify us of the search when entering the Democratic Party office, and entered the office of the vice president of the Institute for Democracy by surprise without revealing their identity,” he said.

Kim Yong, who was in charge of raising funds for the presidential election and managing the organization at Lee’s camp, is suspected of receiving 600 million won ($417,000) and requesting about 2 billion won from former Seongnam Development Corp. planning department head Yoo Dong-gyu in February last year to fund Lee’s presidential election campaign early this year.

Prosecutors arrested Kim on the charges and raided his home Wednesday. After the arrest, he denied all the charges, saying he never asked for nor received money from Yoo.

Lee Jae-myung immediately denounced the prosecution's raid.

"During the parliamentary audit, a terrible thing that has never been seen in the history of Korean democracy, the invasion of the central party headquarters of the opposition party, is taking place,” Lee said on his way to the party’s meeting in Yeouido.

“I hope the people will not forget this historical scene and defend democracy (against) regressing,” he said. Lee was briefly overwhelmed to tears.

The Democratic Party convened an emergency general meeting of lawmakers and temporarily postponed the parliamentary inspection.

Democratic Party lawmaker Oh Young-hwan said in a briefing after the Supreme Council was over on the day, “The state audit has been temporarily postponed.”

"The Democratic Party decided that it would be difficult for us to conduct a normal parliamentary inspection over the surprise raid by the prosecution against the opposition party,” Oh said.

They resumed the inspection in the afternoon, however, but instead said they would not attend Yoon's address to the National Assembly scheduled for Tuesday.

Wrangling over parliamentary address

Amid escalating tensions between the ruling and opposition parties, the scheduled speech of President Yoon Suk-yeol on Tuesday will face a boycott by the Democratic Party.

The Democratic Party is urging Yoon to accept a special counsel probe into Daejang-dong property allegations and to apologize for "oppression of the opposition party," hinting at a boycott of Yoon’s speech at the National Assembly otherwise.

The opposition party held a press briefing Sunday, comparing the current situation to the military dictatorship of the 1980s. They said Yoon oppresses the opposition party through the tyranny of the prosecution.

“We are urging President Yoon Suk-yeol to apologize to the public and the National Assembly for ignoring the National Assembly and oppressing the opposition party. Without even the smallest apology, the Democratic Party will never tolerate the president's speech,” said Floor Leader Park Hong-geun on Sunday.

However, Yoon was dismissive of the demand.

“(The speech) was set for Oct. 25 agreed by ruling and opposition parties. I don’t think I’ve ever heard of any additional conditions attached to it in our constitutional history, as far as I remember,” Yoon said Monday morning when asked about the opposition's demands.

Yoon referred to the clause of the Constitution that guarantees “the president’s right to speak” at the National Assembly and the National Assembly Act that requires lawmakers to “listen to the speech” when the government’s budget plan is submitted.