Remains of some 4,500 people have been found in this grave at Malaga
A Spanish court has suspended the opening of mass graves in the inquiry into the fate of more than 100,000 who vanished under Gen Franco's rule.
The top criminal court ruled by 10 votes to five to stop exhumations from the 1936-39 Civil War.
It imposed the halt to allow it to rule on whether Spain's best-known judge, Baltasar Garzon, had the competence to launch the inquiry.
Campaigners condemned the court's ruling as "brutally inhumane".
"There are many people who are very old who have been waiting for a long time," Emilio Silva, head of the Association for the Recovery of Historical Memory, told AFP news agency.
Judge Garzon announced last month that exhumations could start, including the gravesite of poet Federico Garcia Lorca.
Judge Garzon named Gen Francisco Franco and more than 30 members of his regime as instigators of alleged crimes against humanity.
But the top criminal court, the National Audience, ruled on Friday: "The activities related to the exhumation of bodies must be suspended while this court resolves questions raised by the public prosecutor regarding the competence of the judge to make this move."
Its ruling follows an appeal from the public prosecutor who says Franco-era crimes cannot be examined because of an amnesty law passed in 1977.
Judge Garzon has the support of the United Nations Commission on Human Rights, which recently asked Spain to abolish the amnesty law because it contradicted international treaties.