Former Catalan president Artur Mas has been barred from holding public office for two years after defying Spain's constitutional court to hold a symbolic independence referendum.

The Catalan High Court also banned former vice-president Joana Ortega from office for 21 months and former education minister Irene Rigau for 18 months for defying the constitutional court and going ahead with the non-binding referendum in November 2014.

Mas was also fined €36,500 for staging the vote.

He denied deliberately breaking the law, and took full responsibility for instigating the referendum seeking independence for the region.

"There was no intention of committing any crime or of disobeying anyone," said Mas during the trial, AFP reported. "If it was so obvious that it was a crime, how could it be that the Constitutional Court did nothing to enforce its resolution?"

The constitutional court ruled the referendum unconstitutional days before it was held. It was also opposed by the government of Manuel Rajoy in Madrid.

Around 2.3 million people in Catalonia cast a ballot, with 80.7% voting for independence.