Five members of Sortu (the Basque word for create) declared Monday that the party rejected all violence by separatists, including ETA, but failed to call on the armed group to disband.
On Wednesday, Sortu officially presented the party's charter at the Interior Ministry in Madrid - itself a brave step for a Basque pro-independence group who don't want to be part of Spain.
The party now hopes it will be legally accepted and allowed to field candidates in May's local elections.
The presentation was the culmination of an intense internal debate among ETA-linked, pro-independence Basque groups that concluded in 2010 with a declaration that violence was not the way to seek independence.
ETA's political wing Batasuna was outlawed in 2003 on the grounds that it was part of ETA, considered a terrorist organization since 2003. Since then, the government insists that Basque parties must reject the armed group in order to gain legal status.
Spain, in a law initially drawn up to target Batasuna, insists parties must condemn the use of violence before they can enter elections.
Prosecutors will now determine if Sortu has gone far enough in distancing itself from ETA to gain legal status. Any decision is ultimately up to a special section of the Supreme Court.
ETA, which has killed more than 825 people in a bloody battle for a Basque homeland independent of Spain since the mid-1960s, declared a permanent cease-fire in January. The government, however, insists it must lay down its arms.
Sortu spokesman Inaki Zabaleta told reporters in Madrid that the group was not a continuation of Batasuna, or any other Basque political group, but skirted questions on whether they were calling on ETA to disarm and dissolve.
"We have said that Sortu is a new project, born from a break with the past, which rejects all types of violence. And that is my answer," said Zabaleta.
The new party was unveiled in Bilbao on Monday by a dozen pro-independence activists, including several former members of banned pro-ETA groups and even a former ETA militant, Eugenio Etxebeste, known by his alias Antxon.
The Spanish government gave the party a cautious welcome, with Interior Minister Alfredo Perez Rubalcaba noting it is the first time Batasuna-linked people had explicitly rejected ETA violence.
The minister added that Sortu's followers had little credibility in Spanish society after years of supporting ETA.
ETA's political supporters are desperate to field candidates in the upcoming elections as a way of recovering a pro-independence voice in Basque politics.
ETA is considered a terrorist organization by Spain, the European Union and the United States. In recent years it has been decimated by the arrest of its leaders and operatives, and by dwindling grass-roots support.