For many in Washington, the Sandinista government is composed of radical Marxist revolutionaries. But from his little office here in Managua, Fernando Malespin sees things in a different light.

For him, the Sandinistas are "petits bourgeois" allied with the "structures of capitalism" who have abandoned "proletarian internationalism" and evolved into social democrats afraid to offend European sympathizers, confront the United States and work for genuine regional revolution.

Malespin, a 30-year-old bank accountant turned labor organizer, represents the far edge of a little discussed but increasingly confrontational opposition to the ruling Sandinista National Liberation Front -- the traditional Nicaraguan left.

His hard-line Marxist-Leninist Popular Action Movement, along with the more orthodox Socialist and Communist parties, have sharp ideological and tactical differences with the Sandinista leadership and, according to party officials and foreign diplomats, suffer the same repression as opponents from the right whose cause has been espoused by the Reagan administration.

These differences have sharpened to the point where the leftist parties are meeting with part of the right-wing opposition to seek a common front against some government policies for the first time since the Sandinista revolution took over more than six years ago.

The immediate issue is a renewed and broadened state of emergency decreed Oct. 15 by President Daniel Ortega. Leftist party leaders, echoing colleagues from other opposition parties, say the emergency restrictions were not necessary to confront a U.S.-sponsored insurgency, as Ortega explained, but instead were imposed to stifle political opponents and workers' demands for higher wages.

"If it was directed against counterrevolutionaries, we would support it," said Eli Altamirano, secretary general of the Communist Party Central Committee. "But on the contrary, it foments the counterrevolution. It is directed against the Communist Party, the Socialist Party, the working class."

The afternoon before Ortega announced the toughened restrictions, hundreds from leftist-organized labor unions demonstrated to demand more money, particularly a 13th month of salary traditionally given as a bonus but now suspended. One union leader declared a hunger strike to dramatize the workers' economic plight, party officials said, and was detained by Interior Ministry police.

Nicaraguan analysts said the protest startled the Sandinista leadership. It marked first time such worker demands translated into an open political challenge coming from the left at a government that itself invokes worker welfare as the rationale behind many of its actions, they pointed out. Sandinista government officials said afterward the leftist labor unrest was one reason for the strengthened emergency measures.

Citing the emergency decree, the Socialist and Communist parties last week threatened to pull out of a parliamentary commmission drawing up Nicaragua's new constitution.

On the other side of the spectrum, the Independent Liberal Party already has announced its pullout, also citing the emergency decrees. Juan Manuel Gutierrez, president of the party assembly, said his group has been meeting with leftist party officials for some time to coordinate against the Sandinistas.

Most other parties that oppose the Sandinistas from the right have no representation in the commission or National Assembly. Although their complaints are shared by many Nicaraguans, they refused to participate in elections last November, saying the voting was unfair.

The three parties that oppose the Sandinistas from the left each have two seats in the 96-member assembly, compared to the front's 61. Nicaraguan analysts say this shows many Socialists and Communists have been absorbed by the Sandinista political apparatus. But Altamirano said in an interview that the election results are an inaccurate reflection of leftist political strength here.

"The polling places were manipulated 100 percent by the Sandinistas. The deal was in," he said. "This shows the determination of the Sandinista Front to maintain good relations with capitalist countries in the area by preventing the advance of revolutionary forces in Nicaragua."

On other subjects, however, leftist opposition to the Sandinista government differs sharply from what in the United States is commonly accepted as the opposition.

The Sandinistas' opponents from the right, most of them grouped in an alliance called the Democratic Coordinator, criticize Sandinista rule as usurpation of the 1979 anti-Somoza insurrection by Marxists determined to transform Nicaragua along Cuban lines. These charges largely parallel Reagan administration views.

The left-wing opponents, who strongly oppose U.S. policy, generally criticize Sandinista rule from the opposite direction.

The most severe complaints come from the tiny Marxist-Leninist Popular Action Movement, which now says the government has betrayed what it thought were common leftist ideals.

"A party that has a program of mixed economy and political pluralism and that goes around taking workers prisoner and handing out dollars to the bourgeoisie and landowners, this is not socialism in any part of the world," said Malespin in an interview.

Domingo Sanchez, whose Socialist Party traditionally has been Nicaragua's Soviet-aligned communist movement, said his organization regards the Sandinista Front as the "vanguard" of the revolution but does not consider it is moving the country toward "true socialist revolution."

Altamirano of the Communist Party, which splintered from the Socialist Party in 1967, said the problem is that the Sandinista Front is not controlled by "those elements who are really democratic, advanced and patriotic, who would want to impose a firm policy against North American imperialism.

"The Sandinistas care more about power itself than the use of power to transform society," he declared.