The Spanish government has asked its constitutional court to declare the independence referendum planned in Catalonia as illegal.
Prime Minister Mariano Rajoy said the vote was not "compatible with the Spanish constitution".
Rajoy said "Nobody and nothing will be allowed to break up Spain”, during a televised address to the nation on Monday.
The president of Catalonia, Artur Mas, signed a decree on Saturday authorising a vote on independence on November 9th, for the north-eastern region of Spain.
Signing the decree in Barcelona, Mas said the vote, which is entitled the 'Non-referendum popular consultation on the political future of Catalonia 2014', would be held in line with the Scottish referendum.