National Assembly speaker Moon Hee-sang has stressed the need to promote free and fair trade at a Group of 20 event in an apparent criticism of Japan's export curbs against South Korea.

In his keynote speech at the G20 parliamentary speakers' meeting in Tokyo on Monday, Moon said if the principles of free and fair trade are neglected, the international community won't be able to maintain the basis of co-prosperity through cooperation.

Moon said global trade and investment have contracted and global economic uncertainties expanded by trade spats and protectionism, threatening the free trade order that has achieved sustainable growth and prosperity.

The South Korean speaker called for sustained interest and action by G20 member states to restore the order of free trade.

Moon's four-day trip to Japan to attend the G20 gathering comes amid an ongoing row between Seoul and Tokyo over the latter’s trade restrictions, which appear to many as retaliation for top court rulings ordering some Japanese firms to compensate Korean victims of wartime forced labor.

While Moon seeks to help mend bilateral ties, his Japanese counterpart Akiko Santo is refusing to meet with him, citing the Assembly speaker’s previous calls for the Japanese emperor to apologize for Imperial Japan’s sexual enslavement of Korean women.