Regional barons and disaffected former ministers have been urging that a special congress be called to replace the existing leadership, including Felipe Gonzalez as party leader.
The mutiny was sparked by two recent corruption scandals within the party. In the first, the regional leader in Navarra quit after being accused of siphoning off party funds into his private Swiss bank account.
In the second, an Andalucian party boss was suspended on suspicion of taking money for granting the right-wing mayor of Marbella, Jesus Gil y Gil, unauthorised building permission.
The party was initially relieved after it prevented prevented the conservative Popular Party from winning an outright majority at the polls in March.
But the party has made a feeble opposition debut. Mr Gonzalez said that he wanted to allow Jose Maria Aznar time to establish himself as Prime Minister, and said that he would take a political holiday until September.