Spain has said that it will impose direct rule over Catalonia because the region's leader, Carles Puigdemont, failed to meet a deadline to clarify whether or not he declared independence last week.
This means article 155 of the constitution will be triggered and Catalonia's regional parliament, or Generalitat, will use the right to self-government.
Spain is expected to take direct control on Saturday (October 21).
In an official communique, the Government says it "notes that at 10am, the established deadline, the refusal of the Catalan Generalitat to meet the requirement with which it was issued on October 11, and in which it was required to inform the Government in a clear and precise way if any Catalan authority had declared the independence of this autonomous community and in which it was uarged to restore the constitutional order.
"Consequently, the Spanish Government will continue with the measures laid down in article 155 of the Constitution to restore the legality in the self-government of Catalonia."
The letter went on to denounce "the attitude maintained by leaders of the Generalitat in pursuing, in a deliberate and systematic way, an institutional confrontation despite the serious damage that is being done to the harmony and economic structure of Catalonia."
Puigdemont has ridiculed the Spanish Government for its perceived attempt to repress the Catalan people, and threatened to declare independence if there is no dialogue.
Puigdemont has said "the Catalan Parliament can proceed, if it is considered opportune, to vote for a formal declaration of independence."
Catalonia's unofficial referendum returned an overwhelming majority in favour of independence, with more than 90% voting for secession in the plebiscite on October 1.
In light of this result, Catalan leader Carles Puigdemont declared a mandate for separation and gave a headline speech last Tuesday (October 10) in which he said Catalonia would now begin moving towards separation.
Many were confused by Puigdemont's speech, with some suggesting he had declared independence and others no - leading Spain to demand a clarification.
Spain maintains that the referendum was illegal and rejects any demand for independence.