Giant earth movers slice inexorably into the red soil carried in over the centuries by the Garonne River as it flows gently by the tiny village of Golfech.

The snorts of their diesel engines herald the nuclear-based progress judged indispensable by the new Socialist government in Paris but questioned by many residents of this lush countryside in southwestern France as an intrusion into their lives and their region.

In a broader sense, the powerful machines also symbolize the shift in France's Socialist leadership from an outsider party attracted by generous principles and dissident voices to an elected government wrestling with the hard realities of modern France and armed with a parliamentary majority to make its decisions into national policy.

After campaign promises last spring of a "vast national debate" on the wisdom of pursuing France's swift nuclear power expansion, President Francois Mitterrand's Socialist government has pushed through legislation that, in effect, endorses the previous government's conclusion that France cannot get along without building a substantial network of new reactors.

Ending a four-month freeze on new construction, the Cabinet on Nov. 25 ordered six new reactors begun in the next two years despite significant opposition within the Socialist Party and in regions where the new plants are to rise: Golfech, Cattenom, Chooz, Chinon, Nogent-Sur-Seine and Penly. According to informed French officials, the decision reflected a hard insider's look at French energy needs and fears that delaying the nuclear program would markedly increase unemployment.

The call for reconsidering nuclear power "was a normal opposition tactic," said an official involved in the nuclear program. "But once in power, they have to govern the country."

In October, France's nuclear plants produced 7.6 billion kilowatt hours, or 34.3 percent of its electricity needs, making its program the third largest in the world after those of the United States and the Soviet Union and the first if measured in percentage of electricity needs satisfied by nuclear reactors. Moreover, the industry employs an estimated 150,000 persons in a country shaken by unemployment that has climbed over the 2 million mark despite Socialist efforts to reverse the trend.

"In my opinion, this was the deciding factor," said a nuclear official who followed the government decision from the inside.

Under the program defined by former prime minister Raymond Barre under president Valery Giscard d'Estaing, France by 1990 was to produce 30 percent of its electricity with nuclear power. Under the new program of Prime Minister Pierre Mauroy, the forecast is for 27 percent. This is based on an assumption, doubted by the government's own economists, that the economy will grow by 5 percent a year through the decade, meaning that in all probability the demand for electricity will be less than programmed and the nuclear percentage will be about the same.

"In other words, it's more or less the same program," said an official at the government's Nuclear Energy Commission. "That's why they're screaming so much at Golfech. Nothing has changed."

As a result, the loose and sometimes uncomfortable coalition of young, militant ecologists with traditional local officials in this Golfech region of Cahors wine and Agen prunes charges that it has been betrayed by Mitterrand and his team. The charges are echoed by antinuclear activists at the other sites approved for new reactors.

"We are not only disappointed, but downright disgusted by this treachery," said Claude-Henri Mattei, a leader of antinuclear forces who staged a violent protest here a week ago. "The Socialist republic is a republic of words, a republic of catchy slogans."

In a more concrete expression of bitterness, a group calling itself "the evening bombers" blew up part of a wall surrounding the home of one of the region's Socialist members of parliament early today, leaving behind a pamphlet decrying "the all-nuclear at Golfech and elsewhere." Police in nearby Toulouse said a plastic charge also was planted at the home of a second Socialist member of parliament, but its fuse was put out by rain.

The feeling of betrayal is particularly strong here because hopes were high that the Socialist victory last spring would mean an end to what many local officials and ecology militants considered high-handed tactics by the Giscard government, which chose Golfech for a new nuclear reactor despite a locally organized referendum that rejected the idea by more than 80 percent.

Mitterrand called just before the May presidential election for a "broad national debate" and a referendum to allow French citizens to choose the rhythm of their nuclear construction program. Local antinuclear forces endorsed Socialist candidates largely on the strength of antinuclear positions, and a March 31 letter they say was sent to them by Jean Glavany, today Mitterrand's staff director, promising that construction at Golfech would be halted pending "a vast national debate . . . which cannot be hasty."

Then came the Socialist victory, locally and nationally, and a government decision July 30 to "freeze" five nuclear sites, including Golfech, pending the debate scheduled for October. Many workers assigned to Golfech were transferred to other construction projects, and work on the nuclear plant was halted, according to Electricite de France, the government utility in charge of the project.

But over the summer the idea of a referendum was quietly dropped. The national debate turned into parliamentary consideration of a new law. To overcome Socialist opposition to continuation of the nuclear progam, Mauroy addressed a stormy Oct. 7 party caucus personally and told members they could defeat the legislation only by voting down his -- and their -- government.

The law sailed through 331-to-67. It set up a two-tiered consulation of local officials to meet the objections under Giscard that nuclear sites were imposed despite regional opposition.

In the first vote here, eight of the Golfech region's 16 municipal councils voted against the nuclear plant. Seven voted for and one abstained. But on the broader second level, the Socialist-controlled Regional Council approved the project, despite contrary votes by the region's two main Socialist Party federations only weeks before.

Opponents charged that "telephone calls from Paris" determined the reversal. Mauroy, they pointed out, had said only a short time earlier that, in any case, the government would make the decision.

Even moderate local elected officials complained that their opinions were not really taken into account. As with the ecology activists, they were upset all the more because they believed they had assurances that the Golfech plant would not be built.

Mitterrand "didn't say it straight out, but it seemed clear," said Paul Lafont, the 62-year-old retired schoolteacher who is Golfech's mayor. "This is the reason for the anger. It is a sort of betrayal. There are people, even older than me, who are very angry."