<P> Following the surrender of the Japanese in 1945, civil administration of Papua as well as New Guinea was restored, and under the Papua New Guinea Provisional Administration Act, (1945--46), Papua and New Guinea were combined in an administrative union . </P> <P> The Papua and New Guinea Act 1949 formally approved the placing of New Guinea under the international trusteeship system and confirmed the administrative union under the title of The Territory of Papua and New Guinea . The Act provided for a Legislative Council (established in 1951), a judicial organization, a public service, and a system of local government, with Sir Donald Cleland as administrator . Cleland remained in the position till his retirement in 1967, then remaining in Port Moresby until his death in 1975 . The House of Assembly of Papua and New Guinea replaced the Legislative Council in 1963, and after elections on 15 February, opened on 8 June 1964 . In 1972, the name of the territory was changed to Papua New Guinea . Australia's change of policy towards Papua New Guinea largely commenced with the invitation from the Australian Government to the World Bank to send a mission to the Territory to advise on measures to be taken towards its economic development and political preparation . The mission's report, The Economic Development of the Territory of Papua New Guinea, published in 1964, set out the framework upon which much of later economic policy, up to and beyond independence, proceeded . </P> <P> Elections in 1972 resulted in the formation of a ministry headed by Chief Minister Michael Somare, who pledged to lead the country to self - government and then to independence . Papua New Guinea became self - governing on 1 December 1973 and achieved independence on 16 September 1975 . The country joined the United Nations (UN) on 10 October 1975 by way of Security Council Resolution 375 and General Assembly resolution 3368 . The 1977 national elections confirmed Michael Somare as Prime Minister at the head of a coalition led by the Pangu Party . However, his government lost a vote of confidence in 1980 and was replaced by a new cabinet headed by Sir Julius Chan as prime minister . The 1982 elections increased Pangu's plurality, and parliament again chose Somare as prime minister . In November 1985, the Somare government lost another vote of no confidence, and the parliamentary majority elected Paias Wingti, at the head of a five - party coalition, as prime minister . A coalition, headed by Wingti, was victorious in very close elections in July 1987 . In July 1988, a no - confidence vote toppled Wingti and brought to power Rabbie Namaliu, who a few weeks earlier had replaced Somare as leader of the Pangu Party . </P> <P> Such reversals of fortune and a revolving - door succession of prime ministers continue to characterize Papua New Guinea's national politics . A plethora of political parties, coalition governments, shifting party loyalties and motions of no confidence in the leadership all lend an air of instability to political proceedings . </P>

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