The prime minister and the leader of the ruling conservative party on Sunday jointly announced their plans to fill in for President Yoon Suk Yeol, claiming he will no longer be involved in handling state affairs, in a move denounced by the main opposition as unconstitutional.

In a public address given by Prime Minister Han Duck-soo and the ruling People Power Party Chair Han Dong-hoon, the two said they would cooperate in operational matters related to "national governance." They did announce when any such transition would take place. Han Dong-hoon said they plan to map out the president's "orderly resignation," but did not elaborate on how their decision would correspond with the Constitution.

"President Yoon will not be involved in handling state affairs, including foreign policy, even before his resignation," Han Dong-hoon said in the joint public address.

"We plan to minimize the turmoil (stemming from Tuesday's martial law decree) through President Yoon's orderly resignation," he added.

The announcement came as part of the second meeting between the prime minister and the ruling party leader held after Yoon's surprise decree of martial law late Tuesday.

Regarding the details of Yoon's "orderly resignation," Han Dong-hoon said it will be "swiftly announced after discussions within the (ruling) party." He highlighted Yoon's remarks made at a brief televised address aired Saturday morning, in which the president said he would “leave it up to” his party to “take steps to stabilize the political situation,” including the issue of his term in office. According to Han, "(Based on this remark by President Yoon) there will be no confusion in the process of pursuing the president's early resignation."

Prime Minister Han Duck-soo echoed the ruling party leader's sentiment, saying that the Cabinet plans to take a "humble" stance and work with the People Power Party in "matters related to national governance."

“The administration of state affairs must not be hindered,” the prime minister said, stressing the urgency of passing a national budget to ensure effective governance amid the political uncertainty.

Though the prime minister expressed agreement with Han regarding the need for cooperation between the Cabinet and the ruling party on managing state affairs, he refrained from discussing Yoon's possible resignation in his public address.

The prime minister and the ruling party leader plan to meet at least once every week for the time being to tackle the task of "minimizing the damage" to the people stemming from the current political turmoil, the joint statement read. The meeting between Han Dong-hoon and Han Duck-soo is expected to replace the weekly sessions between Yoon and the prime minister.

The prime minister's office announced in the afternoon that the next weekly meeting between Yoon and Han Duck-soo, originally scheduled for Monday, was canceled.

National Assembly Speaker Woo Won-shik and main opposition leader Lee Jae-myung strongly criticized the ruling camp's plan, both denouncing it as unconstitutional.

Rep. Lee Jae-myung, the Democratic Party leader, said Han proposing to “share the president’s powers is completely baffling.”

“The people elected Yoon, not Han, as president. This is another coup that destroys the Constitutional order,” he said.

Lee said that contrary to Han's claim that Yoon would no longer exercise his presidential power, the president continued to do so when he approved the resignation of Lee Sang-min as interior minister on Sunday.

Lee said he believed Yoon was capable of declaring martial law again “at any moment.”

“It is incredibly dangerous that a man like Yoon still has authority over our military. Yoon must be permanently removed from office through a trial at court,” he said.

Woo Won-shik, the speaker of the National Assembly, said the prime minister and the ruling party leader were violating the Constitution by putting themselves in charge of the country.

“The prime minister and the ruling party’s announcement that they will jointly exercise the powers of the president, which no one has given them, is clearly unconstitutional. It is extreme arrogance, and disrespects the nation's sovereignty and the Constitution,” he said.

Woo said the ruling party and the prime minister were misleading the public with their announcement.

“As the speaker of the Assembly, I am warning you,” he said.

Rep. Kim Min-seok, who is on the Democratic Party's Supreme Council and is considered the main opposition's No. 2 leader, said the ruling party proposal to take over from the president was “unconstitutional and illegitimate.”

“Nobody gave Han Dong-hoon that kind of power. This is just another insurrection,” he said.

Kim said Yoon and all those involved in Tuesday’s martial law declaration should be arrested immediately. That included the prime minister, who was at a Cabinet meeting held right before the president made the martial law announcement, the Democratic Party lawmaker said.

“The prime minister cannot be put in charge of running the country (like this). Not only is it a violation of the Constitution, he is also a main accomplice. He was in a position where he was aware of everything, and yet he let it happen,” Kim said.

Kim also opposed the ruling party's suggestion of Yoon's “orderly and smooth” removal, saying the president needed to be taken down “this instant, as soon as possible.”

“South Korea cannot be safe until Yoon is no longer president,” he said.

The Democratic Party lawmaker said his party would suspend Yoon from office before Christmas.

Yoon on Saturday dodged an opposition-led motion to impeach him at the National Assembly. Most ruling party lawmakers -- 105 of the total 108 -- boycotted a floor vote, which prevented the two-thirds quorum needed for the motion to pass. The main opposition, however, said it plans to "repeatedly" table new impeachment motions against Yoon until one passes.