Barcelona: Catalonia's leader vowed Wednesday that a symbolic independence vote banned by the Spanish government will go ahead on November 9, setting up a constitutional conflict unprecedented in post-Franco Spain.

Defying the latest in a string of legal challenges by Madrid, regional president Artur Mas promised to defend Catalans' "right to decide", despite an order from Spain's Constitutional Court a day earlier to suspend the planned vote.

"We have decided to carry on with this participative process... All peoples have the right to decide their future," Mas said in a speech.

"We are defending fundamental rights protected by basic laws: freedom of conscience, freedom of participation and freedom of expression."

Sunday's vote, which Mas insisted is not a "referendum", will be organised by volunteers without an official electoral roll, but holding it in defiance of the court's veto would put Mas on delicate ground.

"If they go ahead, it will be civil disobedience -- not for the people who vote but for the public officials involved. That is a penal offence," said Yolanda Gomez, a constitutional law expert at Spain's distance-learning university UNED.

Mas had promised to hold the vote in a legal form and watered down plans for an official referendum-style ballot after earlier legal challenges from the conservative government.

Now he has been forced into defying the law in order to keep his promise of holding the vote.

"This time, Mas is going to openly disobey. It is a very complex and delicate matter," said Eduardo Virgala, a constitutional law specialist at the University of the Basque Country.

Pro-independence parties in Catalonia on Wednesday called for the support of the United Nations and European institutions in their standoff with Spain.

In a letter they urged those bodies to "take the necessary action to guarantee that Catalan citizens can democratically decide their future".

Proud of its distinct language and culture, Catalonia has seen a surge in demands for greater autonomy over recent years.

The region of 7.5 million people accounts for nearly a fifth of Spain's economy.

Spain's regions have power over matters such as health and education under the country's constitution, which was passed in 1978, three years after the death of the dictator Francisco Franco.

Catalonia took a step towards greater autonomy in 2006 when it formally adopted a charter that assigned it the status of a "nation".

But in 2010 the Constitutional Court overruled that nationhood claim, fuelling pro-independence feeling.

"The more obstacles they put in the way, the more people will turn out to vote," said Javier Perez Royo, a legal specialist at Seville University. "That will be hard to handle."

But if Catalans go on preparing the vote, Virgala warned: "The government will have two options: appeal to the Constitutional Court again, or prosecute civil servants and the regional government for civil disobedience."

Spain's recent economic crisis has increased unemployment and hardship in the region and swelled its debts, but in 2012 Prime Minister Mariano Rajoy rejected Mas's request for greater powers for Catalonia to tax and spend.

Mas has staked his leadership on the issue, saying a snap regional election could be held to serve as a plebiscite on independence.

Polls have shown that ERC, the hardline nationalist left-wing party that props up Mas's CiU group in the regional parliament, could win a snap election.

"I call on Catalan citizens not to be afraid," Mas said on Wednesday.

"We are doing what it is time to do and what we have to do. We are doing it to defend ourselves, in legitimate defence of a whole people."