31 January 2015 Last updated at 09:39 ET
Tens of thousands of people have massed in central Madrid for a rally organised by radical Spanish leftists Podemos.
The "March for Change" is one of the party's first outdoor mass rallies, as it looks to build on the recent victory of its close allies Syriza in Greece.
Podemos has surged into the lead in recent opinion polls, and says it will seek to write off part of Spain's debt if it wins elections later this year.
Podemos says politicians should "serve the people, not private interests".
The BBC's Tom Burridge in Madrid says that there has been an impressive turnout and a carnival atmosphere at the rally.
Podemos leader Pablo Iglesias spelt out the party's message to the crowd.
"We want change," he said, quoted by the Associated Press. "I know that governing is difficult but those who have serious dreams can change things."
Protesters are parading in the same streets that over the past six years have seen many other gatherings against financial crisis cutbacks imposed by successive governments.
One marcher, Jose Maria Jacobo, told Reuters news agency that people had to fight back against the political class.
"It is the only way..., to kick out all of those politicians who are taking everything from us. They even try to take our dignity away from us. But that they won't take that from us," he said.
Pablo Iglesias with other Podemos leaders on stage at rally - 31 January Pablo Iglesias (C) said people with serious dreams could change things
Podemos supporters attend the 'March for Change' in Madrid The Podemos march takes place amid public anger over spending cuts and allegations of political corruption Banner at Podemos rally reads "is now" - 31 January The party is hoping to build on Syriza's recent successes in Greece
Uncompromising message
Many Spaniards are enraged over reports of political corruption and public spending cuts implemented by the governing People's Party and before that by the Socialists.
The two big traditional parties have described the party - less than a year old and whose names translates as "we can" - as populist.
By threatening to break up Spain's long-established two-party system, Podemos has provided both with a common adversary
Our correspondent says that since Podemos stormed onto the political scene in last May's European elections, it has moved from strength to strength with its uncompromising message against austerity and corruption.
Podemos is a close ally of Syriza and their policies are as radical.
By rallying its supporters today to Spain's famous Puerta del Sol square, the party hopes to send a signal to Spain's traditional parties - and the rest of Europe will be watching, our correspondent says.
Prime Minister Mariano Rajoy warned Spaniards not to "play Russian roulette" by supporting the newcomer, which he said "promises the moon and the sun" but cannot deliver them.
Left-wing and right-wing media have criticised Podemos, accusing it of having ties with Venezuela's left-wing leaders and alleging financial misconduct by some of its senior members.
The party's leaders have in response promised to publish their tax returns, with Mr Iglesias remaining defiant.
"In the face of their hatred, we smile," is one of his regular pronouncements, according to the AFP news agency. After the Syriza triumph in the Greek elections he said that "hope had been born".
Spain has now officially come out of recession but nearly one in four workers remains unemployed.
Last year was the first time there has been full-year economic growth in the country since 2008, when a property bubble burst, putting millions of people out of work and pushing the country to the brink of a bail-out.
http://www.bbc.com/news/world-europe-31072139
