The Spanish government has filed an appeal with the country's constitutional court against a reform passed by the Catalan parliament to fast-track bills through the regional parliament, Prime Minister Mariano Rajoy said Friday.
Catalonia's majority separatist lawmakers hope the reform they approved on Wednesday will pave the way for an independence referendum in the wealthy northeastern region called for October 1 which Madrid deems illegal.
"By presenting this appeal the government is fulfilling its duty to make sure the law is upheld," Prime Minister Mariano Rajoy told a news conference.
"Catalan society needs to be protected from a radical and divisive project which is being imposed on them by force," he added.
"There will not be any referendum on October 1...this is not constitutional and it is not legal."
The reform means that any piece of legislation in Catalonia can now be adopted quickly, with fewer checks and balances.
This in turn should ease the planned passage of a controversial bill that aims to extract Catalonia from Spain's legal system. The idea is to circumvent any legal and practical challenges from Madrid to organising the referendum.
"The sole intention of this reform is to approve through an urgent procedure and without the most basic democratic guarantees laws which aim to liquidate national sovereignty," Rajoy said.
His government has turned to the Constitutional Court with success in the past to get attempts to hold an independence referendum in Catalonia blocked.
The move is only the latest in a long list of defiant announcements, threats and legal challenges from both Madrid and the Catalan executives over its independence drive.
The central government categorically rejects a referendum it says threatens Spain's unity, and which the Constitutional Court has deemed illegal.
But this has fallen on deaf ears among Catalan leaders, who pledge to hold the binding vote on October 1 come what may -- though how they will do so remains unclear.
A majority of Catalans, 70 percent, are in favour of holding an independence referendum, according to the poll by the Catalan government's Centre of Opinion Studies published earlier this month.
But they are divided on the issue of independence with 41 percent in favour and 49 percent against.