Jose Manuel Maza said Carles Puigdemont could be charged with civil disobedience, abuse of office and misuse of public funds for pressing ahead with preparations for the October 1st referendum.
"It's a decision that is possible but we have not considered that we should take it," Maza said during an interview with Onda Cero radio.
Prime Minister Mariano Rajoy, who meets US President Donald Trump in Washington Tuesday, has repeatedly said that the vote -- which his conservative party insists is illegal and unconstitutional -- will not take place,
The legislation underpinning the vote has already been suspended by Spain's Constitutional Court.
Catalonia's leaders retort they have a right to decide their future even if it's not allowed by the constitution.
Madrid has responded with the heavy legal artillery at its disposal to block the vote, dealing a blow to plans to hold a vote with a semblance of legitimacy.
On Monday police summoned 17 people for allegedly developing web platforms dedicated to the banned referendum.
They are accused of allegedly "disseminating a website for people to participate in a referendum declared illegal by the Constitutional Court," a police spokesman said.
Meanwhile police visited the office of the mayor of Oliana, Miquel Sala, one of the over 700 mayors under investigation for pledging to cooperate with the referendum.
Absent at the time, he said his staff handed over only a report compiled for internal use summing up Madrid's position on the vote.
The chief public prosecutor in Catalonia has ordered Catalan regional police, the Mossos d'Esquadra, to go to polling stations on the day of the referendum and identify who is in charge and seize ballots and ballot boxes.
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Polls show Catalans are split on the issue of independence, but a large majority want to vote in a legitimate referendum to settle the matter.
If the "yes" side wins the referendum the Catalan government has said it would declare independence within days for the wealthy northeastern region of Spain, home to about 7.5 million people.
Spain's Foreign Minister Alfonso Dastis told AFP that "a hypothetical declaration of independence won't lead to anything because no one would recognise it."
"They need to stop lying, come back to reason and accept that we will all find a place for Catalonia within Spain," he added before heading to Washington.
Spain's Court of Auditors gave Puigdemont's predecessor, former regional chief Artur Mas, and eight other Catalan officials 15 days to repay the €5.2 million ($6.2 million) in public funds it cost to hold a symbolic independence referendum in Catalonia in 2014 that was also banned by Madrid.
The court said over half of the amount, 2.8 million euros, was used by the Catalan government to buy laptops for polling stations during that vote. If they do not pay the amount by the deadline, the court could seize their
In a joint statement, Mas and the others said the ruling lacked "any kind of legal basis" whose only purpose was to try to "intimidate" separatists.
"We denounce this as an operation of state abuse," they said.
The Catalan regional government has accused central authorities of imposing an "undeclared state of emergency".
By Daniel Silva with Marianne Barriaux / AFP