The Peruvian government may once have had a friend at Chase Manhattan but the results of last Sunday's national election here clearly show that Chase Manhattan doesn't have many friends these days in Peru.

By an overwhelming two-thirds majority, Peruvians voted for left-of-center-political parties that, during the election campaign at least, put costly social programs and theories far ahead repaying the $2.5 billion Peru owes to a consortium of European, Japanese and American banks, including Chase in New York.

Indeed the election results indicate that a substantial majority of Peru's 16 million people are fed up with their current military government, the international debts it has incurred and the economic austerity measures it was forced to impose last month to avoid a massive international default.

Although the election results are still unofficial and incomplete, the patterns have emerged: the left-of-center Popular American Revolutionary Alliance (APRA) of Victor Raul Haya de la Torre was the big winner with close to 40 percent of the vote while the extreme left, composed of Marxist, Maoist, Trotskyite and assorted other socialist parties, came in second with 27 or 28 percent.

The conservative Popular Christian Party of Luis Bedoya Reye came in a close third with 26 or 27 percent while assorted other centrist and conservative parties made up the rest.

The election was solely for a constituent assembly that President Francisco Morales Bermudez has said will only write a new constitution in preparation for general elections promised for late next year or 1980. But the polling also was designed to serve as a sort of national political thermometer after 10 years of military rule and 15 years without a nationwide election.

It appears to have been an accurate sampling and will be difficult for the current government to ignore. Unlike past elections here, not one of the 12 parties that participated last Sunday has charged any voting fraud.

The government harassed the extreme leftist parties - exiling 12 of their leaders, several of whom were candidates, last month after a two-day general strike called to protest the government's austerity measures. But it is difficult to know whether the official harassment helped or hurt the left.

On the one hand, several of the six parties that made up the extreme leftist bloc were without their most prominent leaders in the last weeks of the campaign. Additional arrests may have hampered organizational efforts as well. On the other hand, the harassment may have provoked a certain amount of sympathy for the ultra-left and certainly drew more attention.

[In Washington, the State Department said yesterday it is encouraged by Peru's movement toward a return to democracy despite a severe economic crisis and "political restraints" which preceded the election, Associated Press reported.]

Diplomatic observers here were saying last week that the expected the six extreme leftist parties to receive 15 to 20 percent of the vote. Anything more, they said, would be significant because Peruvians had never before strayed much beyond the moderately leftist - but democratic - ideas of Haya de la Torre's APRA Party.

Although APRA was considered to be quite radical when Haya founded it in 1924, it has, in recent years, occupied a centrist position as a younger generation of leftists - influenced by the Chinese and Cuban revolutions - moved the political spectrum farther to the left.

Nonetheless, while Haya, at 83, may have mellowed over the years and may have wound up closer to the center of the current spectrum, his victory will not necessarily make life any easier for the bankers intent upon collecting their principal and interest payments from Peru's depleted treasury.

During the campaign, Haya demonstrated an incredible agility - both physical and mental - of a man half his age. He attended mass rallies in every corner of Peru, spoke for half an hour at a clip and then thought nothing of sitting with his supporters in various APRA offices until 1 or 2 in the morning. Before the election, he spoke in eloquent generalities and fudged on specifics.

But early Tuesday morning, after his victory was assured, Haya in an interview that lasted more than an hour was more specific. He said he hoped to be elected president of the constituent assembly when it begins work on July 18 and ruled out a coalition with Bedoya's Popular Christians to obtain a majority. Haya said he expects the assembly to be "sovereign wit hall the solemnity of [Peru's suspended] congress" and added that the new constitution should guarantee "economic and social human rights" as well as political freedoms.

Education should be free, public health should be within reach of all Peruvians, public transport should be vastly improved and the government should find jobs for the unemployed, he said.

While these ideas might not raise eyebrows in the United States or Europe, in Peru there remains the question of how to pay for increased social welfare programs - especially at a time when the country must use virtually all of its foreign exchange to pay its debts.

The bankers have warned Peru's current government that it must reduce its public spending if it wants to continue to borrow.

Haya talks of the need to restore confidence in Peru's economy to attract foreign investment. He also talks about increased social welfare. How he and the new constituent assembly balance the two should make life interesting over the next couple of years for Peru's friends at Chase Manhattan and the other banks that pay their $2.5 billion back.