Spain wants good relations with Latin American countries but will not tolerate a lack of respect for its citizens, in this case a prominent one like former Prime Minister Jose Maria Aznar, said Diego Lopez Garrido, spokesman in Parliament for the Socialist Party.
"This is a fundamental, democratic principle, one that governs relations between countries," Lopez Garrido told a news conference.
The spat arose Saturday at an Ibero-American summit in Santiago, Chile, when Chavez accused Aznar of backing a 2002 coup that briefly removed Chavez from power. Chavez repeatedly called Aznar a "fascist" in an address at the summit of leaders from Latin America, Spain and Portugal.
Spain's current prime minister, Jose Luis Rodriguez Zapatero, asked Chavez to be more diplomatic and show respect for other leaders despite political differences. "President Hugo Chavez, I think there is an essential principle to dialogue, and that is, to respect and be respected. We should be careful not to fall into insults," Zapatero said.
Chavez continued to interrupt as Zapatero spoke, although his microphone was off.
A frustrated King Juan Carlos, seated next to Zapatero, leaned toward Chavez and loudly asked, "Por que no te callas?" - or "Why don't you shut up?" The monarch then left the chamber.
Aznar later called to thank Zapatero for defending him, Lopez Garrido said.
Chavez fueled the dispute further on Sunday by suggesting the king knew in advance of the 2002 coup. Spanish royal palace officials were not available for comment Monday.
During the two-day coup in April 2002, Aznar called interim president Pedro Carmona, and the Spanish ambassador to Venezuela met with Carmona. Chavez was restored to power after massive street protests.
Aznar later told the Spanish Parliament he had discussed with Carmona arrangements for Chavez to go to Cuba. Aznar's party has insisted, however, that the conservative government then in power did not back the coup.
But Spain's current Foreign Minister Miguel Angel Moratinos charged in December 2004 that Aznar had in fact given the putsch his diplomatic blessing. Moratinos cited diplomatic cables from the period and other government documents.