Aznar said the planners of the bombings "are not in remote deserts or faraway mountains," El Pais reported.
Aznar's government was ousted three days after 191 people died in the bombings on March 11, 2004. Voters turned to the Socialist Party because they blamed Aznar and his Partido Popular for supporting the U.S. invasion of Iraq, and for focusing on ETA as evidence grew that linked the bombings to Islamists with ties to al-Qaida.
A recent poll indicated that the percentage of Spaniards who believe Islamist terrorists were alone responsible rose by 25 percent during the trial of the accused bombers, to 78 percent, the ThinkSpain Web site reported.
Leaders of Aznar's Partido Popular have distanced themselves from his insistence that ETA was involved.
The Socialist Party has released a video of past statements from the Partido Popular on the bombings. Justice Minister Mariano Fernandez Bermejo suggested Aznar's best course is to "shut up."