This country's small and uneasy white community has given former prime minister Ian Smith's conservative political party a sweeping electoral victory, according to returns announced here today.

Smith, who led the white-minority government of this country, then known as Rhodesia, for 14 years in defiance of international law, won 15 of 20 parliamentary seats in yesterday's special whites-only election with 61 percent of the total vote. The election was widely viewed as a referendum on the future of the dwindling white population here.

The result marks a major comeback for Smith and a stunning rejection of the more moderate and conciliatory stance of a group of independent legislators who broke with him in 1982. The independents had held 13 of 20 white seats in the recently expired Parliament.

Smith's victory, the size of which surprised even his own supporters, indicated widespread disaffection among white voters with the Marxist rhetoric and erratic policies of Prime Minister Robert Mugabe's socialist-oriented government. The victory is almost certain to spark new political tensions between whites, who represent less than 2 percent of the population, and the black majority.

The independents, led by former Smith cabinet member William Irvine, had campaigned on the claim that their cooperative approach offered better protection for white interests than had the confrontational policies and defiant language of Smith and his supporters.

But white voters, many of whom contend that their standard of living has dropped sharply during the five years of black rule even though their privileged economic status in this Third World country has largely been maintained, responded instead to Smith's more emotional and aggressive appeal and his denunications of what he called Mugabe's "communist" policies.

"We need a strong man in that Parliament who won't pussyfoot around the government like these independents," said a white farmer in the southwestern village of Nyamandhlovu as he cast his vote yesterday. "We've got to have someone who'll stand up and tell them what's what."

Voters also seemed to respond to Smith's image as a stern father figure who would protect them from the anxiety and uncertainty that black majority rule represents for many of them.

"You know where I stand," he told a hushed and worshipful audience in the southern city of Bulawayo this week. "I will never bend my principles. I will never abandon you." Smith also had stressed the need for whites to unite. He said today that his party's victory was "a good start towards this goal."

Irvine was one of four members of the Independent Zimbabwe Group, Smith's principal opposition, who won seats. A fifth seat was won by another moderate independent, Chris Andersen, one of two whites serving in Mugabe's Cabinet.

Smith's own reelection was confirmed in early returns last night, but the dimensions of his party's victory only became clear today. It won seats throughout the country, while his opponents won only in this capital city and a nearby eastern rural district, areas where whites generally have maintained a higher level of prosperity since independence. Black officials, who had hoped for Smith's political demise, reacted angrily to his victory.

"The general impression created is that in spite of the spirit of reconciliation, the majority of whites have not changed," said Herbert Ushewokunze, a Cabinet minister and member of the Politburo of Mugabe's ruling party.

Mugabe spent 10 years behind bars under Smith's government for opposing white rule but offered "reconciliation" to the white community after he won the prime ministership in 1980. The two men have not spoken since 1981. Mugabe had no immediate comment on today's results, and it is uncertain whether he will reappoint whites to his Cabinet following Smith's victory. Whites and voters of mixed race retain control of 20 of Zimbabwe's 100 parliamentary seats under the 1979 agreement that led to internationally recognized independence and black-majority rule here. The agreement expires in 1987, when 70 parliamentary votes will be sufficient to abolish or alter the whites-only roll.

Zimbabwe's 2.9 million black voters go to the polls Monday and Tuesday to choose the 80 remaining seats, an election Mugabe's party is considered almost certain to win.