The Spanish Bishops Conference will discuss on April 24 a decree to formally exclude from the Catholic Church and its sacraments those who have helped in ETA's 33-year terrorist campaign, the leading daily El Mundo reported.
If the 85 bishops approve the order, funerals ceremonies for ETA members will no longer be allowed. The last excommunication in Spain was in 1950.
Phone calls to the conference were not answered Sunday.
Madrid Archbishop Antonio Maria Rouco Varela, who proposed the decree, said the church has been heavily criticized in recent years by the government and the media for being too passive in its fight against the separatists, El Mundo reported.
"I have no doubt over the legitimacy of the excommunication order because terrorism is a very serious crime against life and democracy," Rouco Varela was quoted as saying.
ETA, an acronym for Basque Homeland and Liberty, has been fighting since 1968 for independence for the Basque provinces, which straddle the Pyrenees in Spain and France. Since it took up arms, the group has killed around 800 people, mostly security force members, in bombings and shootings.
The Basque region, with a population of 2.1 million and a distinct language and culture, keeps its deeply rooted Catholic traditions, with 40 percent of the Basques regularly attending Mass.
Most ETA members are not church members, but many come from devout Catholic families. The Basque people see their local clerics as the only truly impartial players capable of putting an end to ETA's bloodshed.
Jose Maria Diaz Moreno, a prestigious canonist, told El Mundo that the proposed order is "useless" in stopping the ETA but is "a way to show clearly the Church's stance about the extremely seriousness of terrorism."