Pro-separatist parties, which control the regional assembly in Catalonia, are planning to hold an independence referendum on October 1.
They have already outlined the legal framework for the transition to an independent republic if voters support their bid to split from Spain.
The row over the proposed vote, which is opposed by Spain‘s central government, briefly faded after this month’s ISIS attacks in the region.
Prime Minister Mariano Rajoy’s conservative government in Madrid has vowed to strike down any further secessionist challenges in court.
Spain’s Constitutional Court has already halted attempts to fast-track other preparations for the controversial referendum.
And experts say the court will be asked to invalidate the framework for independence once it is approved by Catalonia’s regional assembly.
The war of words between Catalonia and the central government has escalated in recent days.
Mr Rajoy yesterday called on those in favour of breaking away from Spain to give up their plans.
Days earlier, Catalonia’s leader Carles Puigdemont, accused the central government of deliberately underfunding the region’s security forces.
He said: “We asked them not to play politics with security. Unfortunately, the Spanish government had other priorities.”
Opinion polls have long shown that most people in Catalonia, which has its own language and culture, favour holding an independence vote.
But recent surveys have shown enthusiasm for secession dipping and that fewer than half of Catalans actually support breaking away.
It is not yet clear if Catalonia would be allowed to rejoin the European Union if the wealthy region becomes an independent state.