The Spanish government is seeking to ban a referendum on independence in the Catalonia region by asking the country's constitutional court to declare it illegal.
Prime Minister Mariano Rajoy told reporters that the vote was not consistent with the Spanish constitution.
The head of the wealthy and industrialised Spanish region Artur Mas signed a decree calling for a referendum on independence on 9 November, along the lines of the Scottish vote that took place in September.
Hundreds of Catalans gathered in Barcelona in September calling for their right to vote.
On 19 September, lawmakers in the north-eastern region voted by a margin of 106 to 28 in favour of authorising the referendum.