The Socialists (PSOE) have for months been wracked by internal dissent that has now burst firmly into the open after the party took a drubbing in two weekend regional polls.
This was the breaking point for many high-ranking party officials, as it followed historically low results in December general elections and in a repeat vote in June.
"Seventeen resignations...Were handed in today," a party spokesman told AFP.
A Socialist lawmaker who opposes Sanchez, and refused to be named, told AFP that with two separate, former resignations, this takes the number of party executives that have quit to 19.
Also Read
Sanchez had yet to comment early Wednesday evening.
As Spain's political paralysis drags on following the two inconclusive elections, many within the PSOE want the party to let a right-wing coalition government through parliament by abstaining in the necessary vote of confidence.
That, they argue, would allow them to go into opposition where the party could build up strength again.
But instead the Socialists voted against such a government earlier this month, prompting it to fail, and Sanchez is now trying to form his own coalition with Podemos, the anti-austerity party that wants to replace it as the country's main left-wing force.
"He told me he would go into opposition, that he would not attempt any alternative government," Gonzalez told the Cadena Ser radio station, adding Sanchez had made those comments on June 29, just days after repeat general elections.
"I feel frustrated... As if I had been tricked."
Gonzalez is not the only high-profile Socialist to have come out against Sanchez.
Several of the so-called "party barons" -- or regional presidents -- have also criticised him.
Disclaimer: No Business Standard Journalist was involved in creation of this content