Argentina's military government has arrested the leaders of 25 major labor unions in an effort to crush a general strike they had called for Friday.

The union leaders, followers of the late president Juan Peron and known as the Group of 25, were detained last night by police after the government issued a communique saying that a general strike call would be in violation of the all-encompassing National Security Law, approved by the military junta here after the 1976 coup that overthrew Peron's widow Isabel.

The security law bans strikes and sets prison terms of 3 to 10 years for anyone found guilty of instigating a labor stoppage. Among those arrested was Roberto Garcia, leader of the taxi drivers' union and vice president of the Inter-American Federation of Free Trade Unions.

Most observers, including sources close to President Jorge Videla, said they believed chances of the general strike being carried out as planned had been significantly diminished with the arrests. It was the first call for a general strike since the coup and presented the military government with its most important challenge from workers since it came to power three years ago.

Within hours after the arrests, Economy Minister Jose Martinez de Hoz released figures that he said showed that workers' salaries have increased by more than 9 percent in real terms since the last quarter of 1976. The figures were greeted with skepticism by the press and many economists here, who say real wages have declined by about a third since 1972.

Although the Group of 25 had couched its strike call in economic terms, it also called for release of other labor leaders long held without trial. The government and several high-ranking diplomatic observers said the union leaders' real reasons for confronting the government had more to do with a proposed new "Law of Professional Associations" that would severely curtail union power.

The law would take away union control of medical insurance funds, holiday resorts and pension funds. It would also ban union federations that traditionally have given smaller unions greater power.

"This is all a matter of sheer politics," said one observer. "It comes at a time when the government is trying to break the backs of the Peronist unions on the one hand and trying to open a dialogue with the workers on the other."

While the military government has been making overtures to the union leaders and talking about bringing more civilians into government, the decision to arrest the 25 apparently came because the generals decided they could not tolerate a direct violation of the National Security Law.

Many observers outside the labor movement believe that reorganizing the traditional unions and diminishing their power is necessary to stablize the country. The liberal Buenos Aires Herald editorialized today that "every single person in this country is still suffering the consequences of the strike madness which came to characterize the Peronist labor movement . . . Argentina could do with a long period of recuperation . . ."

The old Peronist union movement has been split into two major groupings since the the military intervened three years ago in the old General Confederation of workers that had been the umbrella organization for all Peronist unions.

The group of 25 is composed of the more militant union leaders who remain loyal to jailed former president Isabel Peron. The larger and less militant National Confederation of Workers did not join the plans for Friday's general strike.

Although accurate membership figures are unavailable, it is estimated that the Group of 25 represents about 1.5 million of the 3.5 million union members who paid dues during the last year of the Peron government. Most of the others belong to newer confederation.