The Lebanese emergency of last summer is not yet over. For many of the poorest residents of that ravaged country, the worst may be yet to come. And the United States, as guarantor of the peace process, will increasingly be held responsible for any new violence, or for further dislocation, hunger and poverty.

What is especially disturbing is that some U.S. private voluntary organizations are contributing to the deteriorating situation, either by remaining silent or by actively increasing social tensions.

A close look at the current situation in Lebanon suggests that the poorest sectors of the population--Lebanese, Palestinians and others of undefined legal status--are being further improverished by continuing events and politics to which the Reagan administration is paying scant attention.

The Lebanese government's official plan is to demolish slum housing this spring along Beirut's southern beaches and near the airport. There is no alternative housing for tens of thousands of Lebanese and other residents who would be evicted in the capital region.

Private Lebanese medical and social agencies are being subjected to a campaign of intimidation by Israeli military forces in the occupied south. This includes visits by armed soldiers to kindergartens, clinics, and vocational training centers, repeated interrogation of local staff on these projects and efforts to turn staff into clandestine informers on fellow staff, clients, and patients.

The announced intent of the Lebanese Forces (the Maronite Christian militia controlling much of central Lebanon) is to drive all but 50,000 Palestinians from the country. There is extensive evidence that many Palestinians are being systematically refused residence and work permits in Beirut. The Palestinian-run Acca Hospital (across the street from the Shatila refugee camp in West Beirut) has been repeatedly harassed. Medicine has been confiscated; work permits for staff have been held up; and would-be patients often fear to enter. Throughout much of the country, there is fear among the refugees that a withdrawal of foreign forces (Israel, PLO and Syria) could trigger a new blood bath in the camps by the same private Lebanese militia groups responsible for the September massacres.

In Northern Lebanon, there are continual outbreaks of chaotic fighting because of Syrian military interference. It is as though a Syrian civil war were being fought by proxy in Lebanon.

Little wonder, under these circumstances, that the poor in Lebanon--regardless of nationality or religion--live from day to day in an atmosphere of deep- rooted fear and insecurity. In such a volatile context, it is disconcerting that U.S. relief agencies are concentrating aid efforts in explicitly religious constituencies. This has the effect of exacerbating the very sectarian tensions that underlie the overall Lebanese social crisis.

One major American organization recently offered to rebuild only those damaged houses belonging to Protestants in a town inhabited by over 90 percent Shi'ite Moslems.

Worse yet is the case of a small coalition of U.S. and European evangelical agencies that has made a formal alliance with the militia of cashiered Lebanese army Maj. Saad Haddad. This group distributes a packet of one blanket, a bag of candy, a New Testament in Arabic and a blue Frisbee to the overwhelmingly Moslem population, while preaching that south Lebanon is part of biblical Israel.

Because political, religious and national considerations have determined who gets help, some groups--for example, the Kurds living in the beach areas of Saint Simon and Saint Michel--have been ignored.

Vigorous support for the following policies could begin to turn the situation around. At the very least, major human disaster can be avoided with:

* An increased focus of aid to Lebanese groups and institutions that have shown they can work with the poorest sectors of the population, or with multinational constituencies;

* A balanced distribution of aid across religious and national lines by all donor agencies;

The provision of housing for Lebanese and other poor people displaced by planned demolitions in the Beirut area.

* The provision of residence and work permits for Palestinian civilians by the Lebanese government;

* Protection for Palestinian medical and social institutions serving the refugee population in Lebanese government-controlled areas (notably the Acca and Ghaza hospitals in Beirut);

* An end to intimidation by the Israeli army of Lebanese social and medical institutions in the southern part of the country;

* The presence of a neutral international force (perhaps by expanding the UNIFIL forces) in all Palestinian refugee camps to protect the refugees against further harassment or further massacres by private Lebanese militias;

* A halt to Syrian military interference in northern Lebanon.

The U.S. government and private U.S. aid agencies have a disproportionate influence on the situation in Lebanon. The question now is whether this influence will be used for good or ill. The entire history of Lebanon argues that there is no middle ground on these issues. If they are not dealt with today, they will be answered for tomorrow.