Sánchez called the snap poll on Monday May 29th after his Socialist party was defeated by the right-wing opposition Popular Party (PP) in local and regional elections a day earlier.
The PP seized six regions that had been led by Socialists although in most of them it will need the support of the far-right Vox party to govern.
The polls were widely seen as a dress rehearsal for a general election that had been expected at the end of the year, but is now slated for July 23rd.
READ ALSO: Who won where in Spain’s regional elections?
In an address to Socialist lawmakers, Sánchez said there is “no difference” between the PP and Vox, and warned they would “dismantle the social progress” made since he took office in 2018.
Among the reforms at risk if the right wins the July 23rd election is a sharp rise in the minimum wage, extra funding for scholarships and a climate change law, he said.
“We have to clarify if Spaniards want to continue with policies that expand rights or if they want to repeal those rights,” the premier added.
“We can’t afford the luxury of giving up even a centimetre of ground.”
The PP – which has for months topped opinion polls – had framed Sunday’s elections as a referendum on Sánchez.
During the campaign, PP head Alberto Núñez Feijóo argued that the vote was an opportunity to “turn the page on ‘Sanchismo’,” a derogatory expression for Sánchez’s policies.
Sánchez has struggled with public fatigue with his government as well as voter disenchantment over soaring inflation and falling purchasing power.
He has also been hurt by the repeated crises with hard-left coalition partner Podemos, as well as by his reliance on Catalan and Basque separatist parties to pass legislation.