The lower house of Spain's Parliament voted 316-5 on Friday to approve a constitutional amendment that would limit future budget deficits.

The proposal is the fruit of a pact between the governing Socialists and the conservative main opposition Popular Party, currently leading in the polls for the Nov. 20 general elections as the jobless rate hovers at 20 percent.

While every PP lawmaker supported the amendment, one Socialist member voted "no," and several other Socialists were among the 30 or so leftist and regional party legislators who walked out in protest prior to the vote.

The proposal to amend Article 135 of the Spanish Constitution is expected to sail through the Senate next week.

The move is bitterly opposed by the left and by Spain's two largest labor federations, which have launched a series of protests leading up to a planned major mobilization next Tuesday in Madrid.

Though the text of the amendment calls for a deficit approaching zero by 2020, it does not specify a figure and the details would be left for a subsequent piece of legislation to be debated and passed by the next Parliament.

The speed of the process and suspicions that the measure is being dictated to Madrid by the European Central Bank and by Germany - the only European Union country with a constitutional deficit limit - have spurred criticism even in the heart of the Socialist party.

Prime Minister Jose Luis Rodriguez Zapatero, who announced months ago that he would not seek a third four-year term, insists the amendment will send a positive message to financial markets.

Unlike some other heavily indebted EU members, Spain is not a chronic deficit-spender and its current shortfall is largely due to emergency responses to the global financial crisis and the collapse of a domestic property boom.