Faced with a significant shift in public opinion against the Panama Canal treaties, the government of strongman Omar Torrijos is unexpectedly finding its public relations campaign in behalf of the pacts as filled with stumbling blocks as the Carter administration's drive in Washington.

The anger surfacing in discussion groups, public meetings and manifestos opposing the U.S. claims to retain military rights here matches the controversy in the United States about "giving away" the canal to Panama.

With 11 days remaining before a referendum on the treaties, there are no polls to gauge the public mood in neat percentages. There is a growing consensus, however, that a number of politically sophisticated Panamanians are firmly against the treaties signed in Washington a month ago.

Yet, there is little doubt that the treaties will gain a comfortable majority among Panama's 800,000 registered voters. Many Panamanians genuinely support the pacts, above all in the countryside where the government's public relations campaign has been largely successful.

Outbursts of criticism among intellectuals, however, suggest the possibility that opposition to the treaties may not end with the Oct. 23 plebiscite.

Some of those opposing the treaties are old critics of the military regime that came to power in a coup nine years ago yesterday. Their main argument is that the long-awaited pact will strengthen Torrijos and perpetuate military rule in Panama.

Many others - nationalists of right, left and center - are deeply disturbed by the neutrality treaty, whose provisions they regard as too vague. They fear it will allow the United States to intervene in Panama in any way it sees fit to protect the canal.

Critics also wonder how Panama can gain the world's respect and run a neutral canal if it gives preference to U.S. warships. These points inspire Panamanians with exactly the reverse fear of those held by American critics who argue that the United States is not receiving sufficient assurances on the crucial issues.

Looming equally large is the charge that the treaties are legalizing the U.S. military bases in the Zone. The fact that the United States had "imposed" these bases on Panama, it is argued, should not force Panama to endorse their presence until the year 2000 with a treaty. Moreover, so the argument goes, there is no timetable for the withdrawal of close to 10,000 U.S. troops stationed here and the United States may find a loophole to keep troops here.

Above many of these concerns over treaty language is a strong fear that the impact of the treaties will mean the militarization of this country, which traditionally has been run by civilians. The treaty calls for $50 million in U.S. military aid for the next 10 years, presumably to prepare the national guard to help defend the canal. Many Panamanians fear this would eventually give Paname a strong army that it does not need, lead to compulsory military service and develop a powerful military caste that, until recently, barely existed here.

Also on the long grievances list is the U.S. plan to offer an economic aid package rather than an outright payment for "lost canal revenues." Aid in the form of U.S. loans would run Panama's troubled economy even deeper into debt.

Torrijos and his negotiators have repeatedly pointed to the negative sides of the pact, but wothout referring to their own leadership.

To avoid charges that the treaty was imposed on Panama, they have granted ample free newspaper space and radio and television time to critics ranging from Marxist student groups to banned political parties on the right. As a result, Panama has enjoyed broad freedom of expression unseen here for the past nine years. The debate has taken place largely in the absence of stongman Omar Torrijos, whose current two-week tour of Europe is seen as a calculated move by analysts here.

Nevertheless, the government has now clearly been taken aback by the growing wave of people openly rejecting the treaty as a "sell-out" and pledging to vote "no" in the plebiscite on Oct. 23. Talk of "panic" in government circles reminded observers here of similar worries in the Carter administration as the anti-treaty offensive mounted in Washington.

Although critism among students and lawyers has been heard here since the treaty texts became known, the trouble became "serious" two weeks ago. In a two-hour television program, the prestigious "Movement of Independent Lawyers" launched the most abrasive well-argued anti-treaty argument yet heard.

"It was electrifying," said an economist, who added that he had been "rather indifferent" about the pact, until then. A secretary working for the government said the effect was =devastating." "It was like a national consciousness raising. "Me and my friends, who aren't political, even started reading the treaties. And the more we read the less we limed it," she said.

The lawyers group, comprising some 300 persons of mixed ideological persuasion, has emerged as the spear-head of the treaty opposition. The lawyers have been comparing the neutrality formulas of the treaty unfavorably with similar documents conceived in other countries, particularly Switzerland. Their argument is that a neutrality "guaranteed" by anyone's military, particularly a superpower, by definition can only have political and no juridical value.

Adding to the stir of the last two weeks, a packed hall of university students yesterday held a shouting match - broadcast on radio - with the negotiations that lasted deep into the night. The Christian Democratic and Social Democratic parties have urged people to vote against the pacts, pointing out that in 1926 and again in 7341. Panama had rejected drafts attempting to legalize the U.S. military bases here. Comparative studies are circulating concluding that a 1967 treaty text, rejected by Torrijos in 1968, was no worse and on some points was more favaroble to Panama than the 1977 version.

As a result, there is a deepening suspicion here that the government is "lying" in its information marathon. Rather then altering the truth, however, the negotiators simply seem to have been pushing the more positive aspect of the pacts. As a diplomat here observed. "Just as Carter's people emphasize what the U.S. is retaining. Torrijos' people are stressing Panama's gains."

The local press widely reports the U.S. Senate hearings on the treaties, and Panamanians were surprised recently to find that a leaked, classified U.S. Embassy cable contained little more than what they had repeatedly heard on their own television sets.

Government spokesmen angrily rebut critics by calling them "stubborn opponents of the government, not of the pacts."

To counteract the impact of the "independent lawyers," the government has hastily formed a lawyers' group of its own, the so-called "Broad Lawyers Front," to defend the treaties on legal grounds. It has also refused requests from several groups for post ponement of the plebiscite to allow for further debate. Officials say that Panamanians know enough about the treaties and only troublemakers want more time.