MADRID — Hundreds of Spaniards demonstrated Sunday against a constitutional reform plan aimed at capping budget deficit.

"No to the reform of the constitution. No to a step back," read a large banner as the demonstrators marched towards Madrid's Puerta del Sol, the hub of months-old protests by the "indignant" youth movement.

Several similar demonstrations were due to be staged in other Spanish cities to demand the constitutional reform be submitted to a popular referendum.

The ruling Socialist and conservative opposition Popular Party have struck a deal on an amendment that would include a budget deficit cap in the country's constitution.

The reform is due to be discussed by parliament during an extraordinary session on Wednesday and needs a three-fifths majority to pass. The Socialists and the Popular Party control around 90 percent of parliament.

"Once again the two major parties made a deal without consulting regular citizens. This cap on spending will only make the situation worse, notably in the education and health sectors," said Pablo Padilla, a 22-year-old unemployed demonstrator.

On August 16, France and Germany had suggested that all 17 eurozone countries adopt laws to balance their budget deficit.

Spain is seeking to slash the public deficit to 6.0 percent of GDP by the end of this year from 9.2 percent in 2010. It aims to reach the EU-target of 3.0 percent by 2013.