The former head of Catalonia's regional government went on trial in Barcelona on Monday accused of defying the authority of the Spanish state and organising a vote on the region's independence.

The five-day trial is likely to inflame longstanding tensions between the central government and the supporters of separatism in the wealthy northeastern region of 7.5 million people.

“I was responsible for the whole thing,” Artur Mas, who stepped down as president of the regional government last year, responded to his defence lawyer after refusing to answer questions from the prosecution in Catalonia’s supreme court.

But, Mr Mas added, the 2014 consultation process would have been impossible to organise without the assistance of 42,000 polling volunteers.

Mr Mas faces a 10-year ban on holding public office if found guilty of disobeying legal authority, abuse of office and misuse of public funds in going ahead with the ballot after Spain’s constitutional court had ruled that it was illegal.