The court on Thursday acquitted the ship's crew and a top Spanish maritime official and awarded no compensation for the 2002 wreck, one of Europe's worst
Its only sentence was a nine-month jail term for the ship's captain for resisting attempts to tow the wreck away from shore before it spilled its load, killing tens of thousands of seabirds.
"The government has decided to launch an appeal, not against the criminal responsibility of the captain of the Prestige, but against the exemption from civil liability," Justice Minister Alberto Ruiz-Gallardon said.
The appeal is "to insist on the need for civil liability, if there is any, to be met by those responsible for the disaster," he told reporters.
The court in the northwestern Galicia region acquitted 78-year-old captain Apostolos Mangouras and chief engineer Nikolaos Argyropoulos, both Greek, and the head of the Spanish merchant navy at the time, José Luis Lopez-Sors, of responsibility for the wreck.
It ruled that deficient maintenance had failed to detect a structural fault that led the ship to break up in a storm. The company that ran the ship was not prosecuted.
When it broke in two after six days damaged and adrift, the Prestige spilled 63,000 tonnes of fuel oil into the sea, coating 2,980 kilometres (1,852 miles) of shoreline in Spain, France and Portugal with black gunk.
The president of the Galicia region, Alberto Nunez Feijoo, explained separately on Monday that the central government's appeal aimed "to recover the money invested by Spain" in cleaning up the spill.
The court ruling put the cost of the disaster at more than €368 million ($494 million) to the Spanish state, €145 million to the Spanish region of Galicia and €68 million to neighbouring France.