South Korean lawmakers are scheduled to vote on an opposition motion to impeach the president for declaring martial law earlier this week.

South Korean President Yoon Suk-yeol has made a public apology for his attempt to impose martial law this week but did not resign, defying intense pressure to step down – even from some in his own party – only hours before a planned impeachment vote.

In a televised address to the nation on Saturday, Yoon said he would not seek to avoid legal and political responsibility for his decision to invoke the emergency measure of martial law for the first time in South Korea since 1980.

He said his decision was born of “desperation”.

“I am very sorry and would like to sincerely apologise to the people who were shocked,” Yoon said, promising there would be no second attempt.

“I leave it up to my party to take steps to stabilise the political situation in the future, including the issue of my term in office,” he said, standing in front of the South Korean flag and bowing after he finished his brief remarks.

The speech was the embattled leader’s first public appearance since he rescinded the martial law order early on Wednesday, just six hours after it was declared and after parliament defied an armed military raid and police cordons to vote against the decree, which forced the president to revoke his order.

Han Dong-hoon, leader of Yoon’s People Power Party (PPP), said after the address that the president was no longer in a position to carry out his public duties and his resignation was now unavoidable.

On Friday, Han had said Yoon was a danger to the country and needed to be removed from power. On Saturday, Han met with the country’s Prime Minister Han Duck-soo to discuss the crisis, South Korea’s Yonhap news agency reported.

Under the constitution, if Yoon resigns or is impeached then the prime minister, who was appointed by Yoon, becomes South Korea’s acting president.

If Yoon leaves office before his single five-year term ends in May 2027, the constitution requires a presidential election to be held within 60 days upon his departure.

Lawmakers are scheduled to vote at 5pm local time (08:00 GMT) on the main opposition Democratic Party’s motion to impeach Yoon. Opposition leaders said if the motion fails, they plan to revisit it again on Wednesday.

Prosecutors, the police and the Corruption Investigation Office for High-ranking Officials have all launched probes into Yoon and senior officials involved in the martial law decree, seeking to pursue charges of insurrection and abuse of power, among others.

Many in South Korea are still reeling from the president’s shock announcement late on Tuesday night, which gave the military sweeping emergency powers in order to combat unspecified threats from “North Korean communist forces”, and “to eradicate the shameless pro-North antistate forces”.

Yoon said martial law was necessary, accusing opposition members in the National Assembly of launching an unprecedented number of impeachment efforts against members of his administration, effectively paralysing key operations of government, and of handling the budget in a way that undermined the fundamental functions of government, including public safety.

Yoon’s move plunged Asia’s fourth-largest economy and key US military ally into its greatest political crisis in decades, and threatened to shatter South Korea’s reputation as a democratic success story.