A working group of the major textile-exporting developing nations concluded a four-day strategy session here with a call for "a significant and substantial liberalization" of international textile trade rules.

Demanding an end to quota restrictions and other "quantitative" protectionist barriers against clothing and fabric imports, the textile exporters group said specialized international textile regulations should be replaced by the "full application of the normal rules and principles of the multilateral trading system."

The proposed reform of international textile-trading rules "is viewed as a test case" for the coming round of global trade negotiations expected to begin next year, noted M. G. Mathur, deputy director of the General Agreement on Tariffs and Trade (GATT), who addressed this week's meeting. "The question that arises is whether negotiations for such trade liberalization are best carried out in isolated form, or in conjunction with an across-the-board effort to open markets and strengthen the multilateral trading system."

In its concluding declaration, issued tonight, the conference skirted the key question of whether the developing-nation bloc will press for an end to a special regimen for textile trading, or simply for a more liberalized version of the present Multifibre Arrangement, adopted in 1974 and scheduled to expire on July 31, 1986.

Sponsored by Mexico and attended by representatives of 21 nations and territories, including the major East Asian textile manufacturing countries, the conference was the latest of a continuing series of meetings aimed at establishing new legal norms for the international textile trade. "Deploring the increasingly restrictive use" of the multifiber accord by the United States and other advanced industrial nations, the delegates stated in tonight's declaration that the trend toward increasing protectionism in the developed world "highlighted the unsuitability of the Multifibre Arrangement."

Developing nations want new rules increasing their access to textile markets in the United States and other industrialized countries while retaining the right to protect their own manufacturers from foreign competition. In a series of economic studies presented to the conference here, they argued that the textile industries of Europe and the United States are highly competitive internationally and do not require the protection they now demand.

A liberalization of textile regulations could be the price of Third World cooperation in the overhaul of the General Agreement on Tariffs and Trade (GATT) now favored by the industrialized nations, observers here suggested.

Many developing countries oppose a continuation of the Multifibre Arrangement provisions that, in contrast to GATT rules, permit restrictive bilateral textile trade accords and quota systems that favor or discriminate against specific exporting nations.

"It is essential to establish a new multifiber agreement that will regulate the marketing of textiles and clothes more equitably," said Luis Bravo Aguilera, Mexico's deputy commerce minister and the honorary conference chairman. Textile trade rules "must be more fair toward the developing nations, who are the principal exporters of these products," he said.

There reportedly are divisions within the bloc of Third World textile exporters, however. While the U.S. quota system limits imports from developing nations as a group, "it also guarantees market access to smaller and less efficient producers, like Mexico, who otherwise might not be able to compete in the United States against the Hong Kongs and the Taiwans," one U.S. trade analyst here said.

"This appears to be an attempt to pressure for changes within the multifiber arrangement, but I'm not sure they all want the arrangement to be ended altogether," said the analyst, who asked not to be identified. The Reagan administration is expected to favor an extension of the present accord with few substantive modifications, the analyst added, noting that the political alternative "would probably be even more protectionist steps like reduced quotas or, even worse, an import licensing system."

The labor-intensive textile and garment business is the largest single industrial employer in the developing world, according to U.N. estimates. Increased sales to consumers in industrialized countries are considered essential to the continuing expansion of Third World textile manufacturing, but retaliation by the import-damaged textile companies of the industrialized nations threatens to close those markets.

Throughout this week's meetings, participants said, the United States was singled out for criticism for its recent tightening of quota-based import rules. Particularly alarming to many delegates were recent U.S. congressional efforts to further restrict textile imports, such as proposed legislation to freeze the U.S. market shares held by foreign exporters of clothing, fabrics, threads, yarn and related goods.