Australia today lifted a ban on mining and export of his vast reserves of uranium, the first step toward becoming leading supplier of nuclear fuel in the final decades of the century.

The country has one-fifth of the West's knows uranium reserves. Shipment would begin in the 1980s to Europe, Japan and the United States, prime Minister Malcolm Fraser told Parliament when announced lifting the four-year mining ban.

The decision was hotly contested by foes of nuclear energy.> However, including the opposition Labor party of former Prime Minister Gough Whitlam - and the government will have to take this sentiment into account in writing mining contracts, to give maximum security against possible sepudiption.

The labor Party favors an indefinits mining moratorium. Its deputy leaders, Tom Urea, declared today: "We say to the mining companies that if you go ahead and sink your $250 million or so time ursnium mining in defiance of Labor policy then doesn't expect any mercy from the next Labor government."

More than a thousan demonstration against uranium-mining gathered outside parliament to hear Uren say that the fight against government policy on the issue had only begun.

Inside the packed chamber, Prime Minister Fraser defended his decision with reference to "dangers of international tension, friction and instability. . . if energy-rich countries like Australia deny resources to those less well-endowed."

By exporting its uranium, valued in tens of billions of dollars, Fraser said, Australia could diminish resort to more dangerous plutonium as a nuclear fuel.

Whitlam characterized the policy as "comparable to the marketing of Thalidomide."

The first Australian uranium is to reach atomic power plants in industrialized countries by 1981 or 1982, initially from deposits of the so-called Ranger Site on the edge of an aboriginal reserve about 125 miles east of Darwin.

[In Ottawa, a spokesman for the Canadian Energy Ministry said the government is pleased with the decision because Australian exports apparently will comply with strict safeguard standards advocated by Canada.]