Despite warnings from China and North Korea, the Japanese parliament tonight approved a pact with South Korea for joint exploration of continental shelf oil resources.

The agreement to search for oil and natural gas in a area of the East China Sea located between the tip of South Korea, Japan and China was signed three years ago. Angered by the delay in ratification, South Korea has accused Japan of a breach of faith and has threatened to start unilateral test drillings.

Japanese opposition parties blocked five previous attempts to win parliamentary approval of the controversial bill. It was finally passed by the lower house May 10 and automatically became law at midnight tonight when a specially-extended session of the upper house failed to take action.

China has criticized the pact as "absolutely unacceptable. Peking has warned that it would harm development of friendly relations between China and Japan and said the pact infringed China's sovereignty.

North Korea has branded the joint development agreement as a criminal document and demanded that Japan abandon "illegal ratification."

The Tokyo government's determination to placate the impatient South Koreas has involved it in internal discord and dispute with China and North Korea over still unproven oil deposits. A.U.N. report has speculated about, but not confirmed, the possibility of oil in the area. The 1973 oil crisis spurred development of all possible energy resources here and Japan and South Korea signed the exploration and development pact in January 1974. The South Korean National Assembly ratified it soon after.

Japanese Socialists and other opposition groups have successfully stopped ratification attempts for three years on the ground that it would create diplomatic difficulties with China and North Korea, risk ocean pollution, and increase ties between Japan and South Korea that they consider corrupt.

Japan's share of the oil deposits would be less than one year's fuel oil consumption. Even if oil is located in commercial quantities, exploitation may be difficult. The seabed is 600 feet deep, close to the commercial extraction limit, and the area is traversed by rapid currents.

Three wholly-owned subsidiaries of major American oil companies - Gulf, Shell and Texaco - have contracted with the South Korean government for drilling rights. Gulf oil has admitted making donations of 4 million to South Korean President Park Chung Hee's Democratic Republican Party. The U.S. gorvernment has advised the American companies against drilling in an area where China claims sovereignty.