Rival parties continue to wrangle over North Korean coal imported into South Korea even after the Korea Customs Service on Friday announced related probe results and legal action to follow.

The main opposition Liberty Korea Party demands a parliamentary probe into what it calls the "North Korean coal gate." A party spokesman said Saturday it is a serious matter that directly relates to South Korea's global credibility, and must not be glossed over as the sole responsibility of the importers.

The minor opposition Bareunmirae Party also said the government has confirmed the illegal coal imports ten months after they happened and public suspicions are not resolved.

The party criticized the government's late response and called for a parliamentary investigation.

The ruling Democratic Party meanwhile said the opposition camp was launching a political offensive. DP's floor spokesman Kang Byung-won said the Liberty Korea Party was deliberately ignoring the facts and context of the issue.

Kang clarified the fact that the government obtained intelligence last October and jointly investigated the matter with the United States. He emphasized that the government has decided to hold accountable the firms that have violated UN sanctions on North Korea.