Zapatero said it was a "clear mistake" saying that the violence associated with ETA attacks had subsided in the last five years, EFE news agency reported.
One day after the prime minister's remarks in late December, a bomb blamed on ETA exploded at the Madrid airport, killing two people.
For three decades, ETA militants have been fighting for a Basque homeland along the French-Spanish border. Their attacks have claimed some 850 lives.
Celebrity Families of 2014 [PHOTOS]