Minister Malcolm Fraser's decision today to call a national election only halfway through his term plunged Australia into what is expected to be a bitter campaign.

Fraser announced in Parliament that an election will be held Dec. 10, and the plan was immediately improved by the Governor General, Sir John Kerr. The announcement was not entirely unexpected; for the past month, Fraser has been feeding speculation that he was planning a December election.

Opposition leader Gough Whitlam, a self-styled democratic socialist who served as Prime Minister from 1972 to 1975 when he was dismissed by Kerr accused Fraser of timing the election to beat an anticipated sharp downturn in the country's economy.

Australia's economy has been stagnant for most of Fraser's two-year rule. Although there have been signs recently that the inflation rate is edging under 10 per cent, unemployment is at a record of 4 percent and real economic growth is virtually non-existent.

Unemployment is expected to worsen next year and opinion polls indicated that Fraser could win reelection in December with a comfortable majority, but might lose if he waited until 1978.

The personalities involved in today's decision were a dramatic reminder to Australia's eight million voters of Nov. 11, 1975, when Kerr dismissed Whitlam's Labor Party government, using a vice-legal power that no previous Australia governor-general had dared exercise.

Fraser was swept to power in December 1975 election following Whitlam's dismissal.

Fraser called the election in the midst of one of the country's disruptive labor disputes in recent years. A three-month strike by power workers in the key industrial state of Victoria threw half a million workers out of their jobs and cost billions of dollars in lost production.

Just before he called the election, Fraser enacted tough new labor legislation which imposed harsh penalties on unions whose strikes disrupt the economy.

Fraser plans to use union militancy as the central theme of his campaign. His slogan is expected to be: Who Is running the country, the government or the union?

Fraser is more completely in command of his coalition of conservative parties than any leader since Sir Robert Menzies, who ran Australia from 1949 to 1965.

Whitlam, at 61, is 14 years older than Fraser and no longer has the undivided support of the Labor Party - which swept him to power in 1972 on a promise to move Australia gently to the left.

Whitlam does have the support of the bulk of the powerful Australian union movement and the young trendsetters in Australia's hedonistic middle class. He is also a more persuasive orator and a quicker thinker on his feet than Fraser - a sour, serious and very rich farmer who has win more respect than royalty from Australian voters.