In a letter to Secretary-General Kofi Annan on Wednesday, Pak Gil Yon - North Korea's UN ambassador - said that "considering its [Japan's] past crimes against humanity, today's revival of its militarism and threats to neighbouring countries, Japan's permanent membership of the UNSC cannot be tolerated at all as it contravenes the main mission of the United Nations.
UN officials and Japanese and North Korean diplomats in New York had no immediate comment on the letter, which was dated Monday and first reported by China's official news agency Xinhua.
The letter was sent as ambassadors from Japan, Brazil, Germany and India met with Annan to press their case for permanent seats for all four nations should the council be expanded from its current 15 members.
The four have agreed to support one another's candidacies as the United Nations debates a possible enlargement of the council later this year.
Japan occupied Korea in 1905 following its victory in the Russo-Japanese War and annexed the entire peninsula five years later. At the end of World War Two, a republic was set up in the southern part and a communist-style government in the north.
"Considering its past crimes against humanity, today's revival of its militarism and threats to neighbouring countries, Japan's permanent membership of the UNSC cannot be tolerated at all as it contravenes the main mission of the United Nations"
Pak Gil Yon
North Korea's UN ambassador
Pak's letter said Tokyo "committed most heinous destruction, plunder and homicide everywhere in Asia" including in Korea during the war and now hoped to again dominate Asia.
North Korea, "strongly opposes an expansion of the UNSC which includes Japan's membership," he wrote.
The council currently has five permanent members with veto power - the United States, Britain, France, Russia and China - which have held their seats since the United Nations was formed in 1945. The other 10 members are elected for two-year terms.
Most UN members consider the council's composition outdated and unrepresentative. But any change in its membership structure would require the approval of two-thirds of the 191-nation General Assembly and no veto from the five permanent council members.