MANILA, OCT. 14 -- The government of Philippine President Corazon Aquino faces a growing threat from a restive labor force that has called a series of nationwide strikes and disrupted several economically strategic industries.

While most of the strikes are over wages, a number of illegal, leftist-inspired strikes have posed a direct political challenge to the government. Business leaders are pressing Aquino to show more resolve in enforcing labor laws, even if it means arresting the leaders of illegal strikes and breaking up illegal barricades.

Earlier this week, police fired guns in the air and arrested more than two dozen union leaders in isolated incidents to dismantle workers' barricades at the beginning of a planned nationwide strike over low wages. Yesterday, about 5,000 workers waving red flags and lighted torches defied armed police to march to the presidential palace.

Many business leaders and foreign diplomats view the mounting labor problems as potentially more damaging to Aquino and her efforts to revive the economy than the communist insurgency and continuing threats of a military coup. Despite the labor strife, the economy has grown impressively -- at least 5 percent in the last quarter compared to the same period last year. But analysts say the widespread strikes are frightening away foreign investment needed to sustain the recovery and create new jobs.

Most worrying for business leaders here is that a growing number of the strikes appear to be politically motivated. Many walkouts, such as yesterday's, are led by a communist-infiltrated labor federation, the May 1st Movement, which is believed to receive funding from the Soviet Union and leftist unions in Western Europe and Australia. Its political agenda includes a crusade against foreign multinational corporations, the removal of perceived "fascists" from the government and the dismantling of American military bases.

In the view of military officials and foreign business analysts, the ultimate aim of the May 1st Movement is to use work stoppages to topple the Aquino government. Labor Department statistics show that the number of strikes is down over last year, but businessmen and foreign analysts say the leftist-inspired strikes have been strategically targeted to disrupt the economy.

"It is now come to a state where we are diagonally opposing the government," said Roberto Ortaliz, secretary general of the May 1st Movement. "We are taking advantage of the so-called democratic space now. We are also taking advantage of the liberal stance of the government."

A western diplomat called the strikes "a serious impediment to investment."

Most of the strikes, such as the week-long series of coordinated nationwide protests that began Monday, represent an effort by workers to make up for the drop in wages and purchasing power during the past four years of recession. Union officials estimate that workers' purchasing power has declined by about 20 pesos, about $1, per day, since October 1984. A western diplomat estimated that the average worker's purchasing power has fallen below the 1972 level.

In addition, prices of basic commodities, such as rice, have increased.

After years of repression under former president Ferdinand Marcos, labor leaders say their workers have grown assertive and are more willing to strike as a first option in a labor dispute.

"The advent of rising prices has made the suffering unbearable," said Democrito Mendoza, president of the moderate Trade Union Congress of the Philippines. "The gap has become wider and wider and, after a certain point, it becomes like a volcano which has to erupt. It is erupting now."

The strikes are aimed at pressing Aquino into issuing an executive order granting all workers an across-the-board 10-peso, or 50-cent, increase in daily wages. Aquino has proposed increasing only the minimum wage, by eight pesos, and she has said unions must learn to bargain collectively for their pay and not to rely on a strongman president, such as Marcos, to set wages.

That posture, however, was undercut when Aquino agreed to push for an increase in the basic pay of soldiers following an unsuccessful military coup attempt Aug. 28. The prospect of a pay raise for the military has incensed the workers.

But the frustration over low wages has come to be identified lately with other political issues.

The May 1st Movement has staged strikes at a number of key food-producing plants, including Nestle Philippines. Those companies pay their workers the highest wages in the country, usually more than twice the minimum wage. Business leaders and experts say they suspect that the real aim of the strikes is to create food disruptions in the capital and destabilize the government at a time of political uncertainty.

"The strikes are not based on any rational economic policy," said a western business analyst who advises foreign firms here. "Their sole purpose is to disrupt."

The movement's secretary general, Ortaliz, acknowledged in an interview that many economic and political issues go "hand in hand."

Because of continuing foreign domination of key natural resources, he said, "social justice" is being made an issue in movement-inspired labor disputes.

Most Philippine military officials, business leaders and foreign diplomats consulted say the militant labor union has direct ties to the Communist Party of the Philippines. The founder and first chairman of the May 1st Movement, Felixberto Olalia, drifted in and out of the former Partido Komunista ng Pilipinas.

Asked about the communist connection, Ortaliz said "red-baiting" began under Marcos to discredit the union when it was formed six years ago. But, Ortaliz added, "we could never deny the natural link between the workers and the people involved in armed struggle." He said some union members and officers "may be" members of the National Democratic Front, the Communist Party's front group.

Ortaliz said the union began its international fund-raising drive in 1982, soliciting funds from sympathetic unions in Western Europe and Australia. At one point, he said the accusation that the union received Soviet funds was "a blatant lie." But at another point, he said, "Our official linkage with the Russian trade unions started only this year."

In February, union chairman Crispin Beltran traveled to Moscow and Bulgaria on what diplomats believe was a fund-raising mission.

The May 1st Movement is a federation of various unions and is not registered as a separate union with the labor department. Thus, the funds coming to the federation from abroad are not registered or accounted for by any government agency.

The group is believed to use its funds to sustain long strikes, often by paying striking workers as much as 50 pesos a day, only four pesos short of the minimum wage. It claims to have more than 600,000 members, although western diplomats put the figure closer to 150,000.

The Aquino government recognized the May 1st Movement after coming to power in the February 1986 revolution.

Through its vocal union militancy, the group has managed to preempt its rival, the more centrist Trade Union Congress of the Philippines, allied with the AFL-CIO, on some bread-and-butter worker issues. The Trade Union Congress claims more than 1 million members, but diplomats put the figure closer to 500,000.

The May 1st Movement has succeeded in forcing the progovernment Trade Union Congress into a more militant posture, forging a "tactical alliance" over issues such as the need for a 10-peso-a-day wage increase.

Such an alliance poses a serious challenge for the government. The last time the two groups agreed to a joint strike, on Aug. 26, they succeeded in paralyzing Manila and several other urban centers.

"The {Trade Union Congress} has grown more militant," said a diplomat. "It had to, in response to the {May 1st Movement}. They've got this militant competition." During this week of nationwide strikes, the diplomat said, "the two {unions} could shut down Metro Manila."