Spanish Prime Minister José Luis Rodríguez surprised Congress on Tuesday by proposing the inclusion of a cap to the public deficit in the country's Constitution.
Zapatero said he had spoken about the planned constitutional amendment with the leader of the main opposition Popular Party (PP), Mariano Rajoy, and the Socialist's candidate for the general elections on November 20, former Interior Minister Alfredo Pérez Rubalcaba, both of whom support the initiative, which the prime minister said would help the process of fiscal consolidation and "strengthen" confidence in the Spanish economy in the medium to long term.
"I think it is possible to reach an agreement on constitutional reform, and I invite the two major parties and the other groups in parliament to draw up a draft law that could be approved immediately," Zapatero said during a debate on the latest batch of austerity measures by the government as part of its efforts to convince the markets of Spain's creditworthiness.
During the debate Rajoy said the PP backed the idea of enshrining the need for fiscal propriety in the Constitution and said the party was willing to help ease its way into legislative form. "I believe we should have done this before, and things would have gone better for us," Rajoy said.
European Commission spokesman Amadeu Altafaj also welcomed Zapatero's "political commitment" to fiscal discipline.
The idea of constitutional brakes on euro-zone member debt levels was broached by German Chancellor Angela Merkel during her summit meeting on August 16 with French President Nicolas Sarkozy.
The central government in Spain already has a law that puts a ceiling on growth in public spending in line with average expected economic growth. The country's regions have been asked to adopt similar rules for their public finances.
The government managed to cut its public deficit from 11.1 percent of GDP in 2009 to 9.2 percent last year, and is aiming to trim it further to six percent through an austerity drive that was extended last week by budget savings of a further five billion euros this year.
The new measures were introduced after a renewed attack on Spanish and Italian government bonds that drove the risk premiums of the two countries to euro-era record highs - of over 400 basis points in the case of Spain.
The spread between the yield on the Spanish benchmark 10-year government bond and the German equivalent has eased to under 300 basis points in the wake of the European Central Bank's program of buying the sovereign debt of euro-zone countries in problems in the secondary market.
"This decisive action [by the ECB] has helped relieve the tension, particularly in Spain and Italy, but this is transitory and exceptional and we have to continue working to make it unnecessary," Zapatero told Congress.