A nationwide gathering of rebellious Episcopalians today signed themselves out of the Episcopal Church and issued a continentwide challenge for like-minded folk to join them in creating a new and "pure" Anglican Church in North American.

An "Affirmation of St. Louis" issued at the closing session of the three-day Congress of Concerned Churchmen called for a new church which would bar women from the priesthood, outlaw divorce and extra-marital sex, shun the World Council of Churches and other ecumenical alliances, and concentrate on spiritual rather than social and economic concerns.

A constituting convention for the new church is targeted for sometime next year.

The six-page affirmation insists that it is not the dissidents who are schismatic, but the established Episcopal or Anglican churches "by their unlawful attempts to alter faith, order and morality" through actions taken at church conventions in recent years.

The congress, with nearly 1,800 registrants, is the largest gathering of dissident Episcopal Church members to convene since the church voted a year ago to ordain women into the priesthood. That action, and a similar move by the Anglican Church of Canada a year earlier, crystalized opposition in both churches among those who perceived a trend to secular humanism. Thus the secessionist movement was born.

The St. Louis congress here brought together 14 different groups to lay strategy for setting up their own "traditional Anglican church."

One of those groups, meeting separately after the main congress session, elected the first separatist bishop.

He is the Rev. James O. Mote, 55, of Denver, who last November became the first priest in the Episcopal Church to pull his parish out of the national denomination in protest over the issue of women priests.

But Mote, who was elected by a secessionist group called the Diocese of the Holy Trinity, still faces the problem of getting himself consecrated, a rite which requires the participation of three validly consecrated bishops.

Leaders of the breakaway diocese have been unable to locate more than two who are willing to help - retired bishop Albert A. Chambers of Springfield, Ill. and Clarence H. Haden Jr., bishop of Northern California. Both could face disciplinary charges from their fellow bishops in the Episcopal church by consecrating a bishop for the renegade church.

The congress here was carefully programmed to generate maximum support for secession and a minimum of discussion of alternatives. The affirmation document itself was subject to neither discussion nor vote. It was simply read to the assembled body which responded with a standing ovation. Participants were urged to sign it themselves and work for additional signers back home.

Estimates by leaders of the gathering of the potential strength of a breakaway church varied widely - from 5,000 persons to 500,000 persons.

The six-month-old Diocese of the Holy Trinity, a non-geographical jurisdiction functioning as a sort of catchall diocese until the new national church is formed, includes 23 parishes, and admission applications pending from more than 30 more, a spokesman said.

In addition to the deep emotional attachments many Episcopalians feel for their church, one strong deterrent to parishes leaving the fold is the prospect of long and costly legal battles over ownership of parish property.

While women priests and controversial revisions in the Book of Common Prayer were undoubtedly the straws that broke the camel's back in the current crisis, today's rebellion has been a long time growing.

The ringing anti-establishment rhetoric here this week has assailed everything from the church's failure to hang a heresy charge on the late Bishop James Pike to Elizabeth Taylor's latest marriage - performed by an Episcopal priest despite her numerous divorces.

The Rev. George William Rutler of Rosemont, Pa., told the gathering: "We are waging here nothing less than the battle between Christianity an secular humanism."