The ruling Saenuri Party stepped up pressure Tuesday on the main opposition Democratic United Party(DUP) to help discipline opposition lawmakers accused of sympathizing with North Korea.

In a radio address, Saenuri chairman Hwang Woo-yea urged the DUP to take punitive measures against Rep. Lim Su-kyung, an activist-turned-lawmaker who made headlines in the past week for calling North Korean defectors "traitors."

"There is a lawmaker who caused public anger and astonishment for calling defectors traitors," Hwang said as he recommended the lawmaker's party "take due disciplinary action."

Hwang said it is the duty of South Korea to treat North Korean defectors with respect and welcome them as they will be future leaders when Korea reunifies.

Lim made her comment and other remarks during an impromptu meeting with a defector-turned-college student at a bar on Friday, according to a Facebook posting by the student, Baek Yo-sep.

Lim offered an apology Sunday, claiming she never meant to describe defectors as traitors. Her apology did not quell public criticism, especially among the 23,500 former North Koreans now living in the South.

She made an unauthorized trip to Pyongyang in 1989 and met with then leader Kim Il-sung, the communist regime's founder and the grandfather of current leader Kim Jong-un. Pyongyang called her the "flower of unification" at the time.

Representatives of North Korean defectors called on Lim to voluntarily resign.

Lim's insult revealed the pro-North Korea stances of some politicians and reignited a controversy over how to deal with the communist neighbor, they said.

Several groups of defectors visited the National Cemetery in southern Seoul, a day before Memorial Day, to honor those who paid the ultimate price for the country's freedom and liberation.

The visit serves as an occasion to renew "our commitment to root out 'jongbuk' forces who deny South Korea's identity," the defectors' groups said, referring to pro-Pyongyang followers.

Also Tuesday, Rep. Lee Hahn-koo, the floor leader of the Saenuri Party, pressed the DUP again to cooperate to oust Lee Seok-gi and Kim Jae-yeon, two lawmakers from the left-wing minor opposition Unified Progressive Party (UPP), from the National Assembly.

The lawmakers were convicted of engaging in pro-North Korean activities in the past and allegedly espoused North Korea's guiding "juche" philosophy of self-reliance. They are also accused of being involved in the UPP's alleged rigged primary designed to select proportional representation candidates for the April parliamentary election.

Lee of Saenuri said his party can be flexible in its negotiations with the DUP on which party will control key parliamentary committees if the DUP agrees to pass a parliamentary resolution calling for the release of a South Korean man detained in China, and to strip the two lawmakers of their seats.

The latest call comes amid widespread concern the lawmakers' alleged pro-North Korea beliefs could pose a threat to national security. 

Lee of the UPP on Tuesday reaffirmed he has no intention to quit his seat. "I have said consistently that the truth (of the alleged primary fraud) should be revealed first," he told reporters. Lee described a possible expulsion as killing by legislature. Kim has also refused to quit her seat.

An ouster requires two-thirds approval from the 300-member National Assembly. The Saenuri Party and the DUP have 277 seats combined.

Former Prime Minister Lee Hae-chan, now a DUP lawmaker running for the party's chairmanship, has somehow joined in the pro-North Korea row, as he on Monday called for a hands-off policy toward North Korea's human rights issue.

Lee further triggered a controversy by expressing anger over being questioned about Lim's insult during a live radio interview on Tuesday.

Lee complained to the radio host for asking questions on Lim and a recent bill calling for the improvement of North Korea's human rights conditions. Lee later abruptly hung up the phone during the interview.

Lee, who served as a prime minister for a previous liberal government, was under fire for his recent remarks that the bill on North Korea's human rights could be an interference of North Korea's internal affairs.

Hwang of the Saenuri Party supported foreign intervention in a country that abuses human rights of its citizens, saying, "We should draw a clear line and set a clear principle" on the issue of human rights.

He said in a meeting with Saenuri lawmakers that people's human rights and free and democratic order are among the most important issues in terms of constitutional values.

Rep. Ha Tae-kyung of the Saenuri Party, whom Lim also denounced for being a traitor, said the former prime minister appeared to have made a mistake.

Some opposition lawmakers have shied away from the issue of the North's dismal human rights record out of fear that it could worsen inter-Korean ties. (Yonhap News)