Spain's constitutional court has suspended next Monday's session of the Catalan parliament, in a bid to pre-empt a possible push for independence.
The court said such a move would be "a breach of the constitution".
Earlier, Prime Minister Mariano Rajoy warned Catalonia's regional government against declaring independence after a disputed vote last Sunday.
Catalan leader Carles Puigdemont had indicated that he could make such a declaration at next week's session.
The speaker of the region's parliament, Carme Forcadell, said the constitutional court's ruling on Thursday damaged freedom of expression and showed how the courts were being used to solve political problems.
But she said the parliament had taken no decision yet on whether Monday's session would go ahead.
The ruling upheld a challenge not from the government in Madrid but by the Socialists' Party of Catalonia which opposes secession from Spain.
Allowing the regional parliament to meet and declare independence, the court said, would violate the rights of the party's MPs.
An earlier ruling by the court aimed at stopping Sunday's vote was ignored by Catalonia's leaders. That challenge to the court had come from Spain's government, which condemned the referendum as illegal.
The socialists won almost 13 percent of the vote in the 2015 election, and have 13 MPs in the 135-seat regional parliament.
Organisers of Sunday's vote put the turnout at 42 percent with 2.2 million people taking part. They say 90 percent voted for independence, however they have not published final results. There have been several claims of irregularities.
There was violence at polling stations as police, trying to enforce a Spanish court decision to ban the vote, attempted to seize ballot boxes and disperse voters.
Also on Thursday, the board of Sabadell, a major bank, decided to transfer its headquarters from Barcelona to the south-eastern Spanish city of Alicante.
CaixaBank, another large Barcelona-based institution, is reported to be considering a similar move. This would ensure the banks remained within the eurozone and under the supervision of the European Central Bank.
How the crisis escalated:
- 1 October: Catalonia holds banned referendum on independence, defying Spanish government and a Constitutional Court ruling; Catalan leader Carles Puigdemont says the independence camp has won
- 2 October: The European Commission says it regards the referendum as illegal and an independent Catalonia would be outside the EU
- 3 October: In a TV address, King Felipe says referendum organisers showed "disrespect to the powers of the state" and broke the rule of law
- 4 October: Mr Puigdemont says a declaration of independence will come within days; the government says it will not give in to "blackmail"
- 5 October: Spanish PM Mariano Rajoy urges Catalan leaders not to declare independence. Constitutional Court bans session of Catalan parliament due on Monday.