The suit was passed on to the Supreme Court on Tuesday by a lower court where it had been under review in light of controversial new legal protections for ex-king Juan Carlos, 76, who lost his total immunity when he quite the throne last month, she said.
It was brought by Alberto Sola Jimenez, 58, an adopted child who has claimed for years that his birth mother, the daughter of a well-known Barcelona banker, may have had an affair with the king before he married Queen Sofia which resulted in his birth.
Sola, who used to run a successful metal firm in Mexico and now works as a waiter in the village of La Bisbal in northeastern Spain, appealed that verdict.
Juan Carlos automatically lost the total immunity which he enjoyed during his 39-year reign when he abdicated on June 18, leading lawmakers to rush in controversial new legal protections for the ageing former monarch.
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He now must answer to Spain's highest court, the Supreme Court, which has a high threshold for evidence, giving him similar protection enjoyed by many high-ranking civil servants and politicians.
Sola's paternity suit is the first legal challenge to be filed against the former monarch at the Supreme Court since he lost his total legal immunity.
The court will now have to decide whether it accepts the suit or shelves it.
Sola and Sartiau made headlines in Spain in 2012 when they teamed up and underwent DNA tests that showed there was a 91 percent chance that they had one parent in common.