Political parties in Catalonia Tuesday called a mass demonstration for next month to protest changes by the country's highest court to a charter that gave the regional government sweeping powers.

The Constitutional Court, responding to a legal challenge to Catalonia's "statute of autonomy" by Spain's conservative opposition Popular Party, upheld most of the charter but struck down a number of controversial points.

The four-year-old statute expanded the already significant powers of self rule of the government of Catalonia, where a sizeable minority would like to see the wealthy northeastern region, which has its own language and distinct culture, break away from Spain.

The head of the regional parliament, Ernest Benach, said the court's ruling had opened up a "state crisis."

Political parties, unions and Catalan cultural associations called a mass protest for July 10 in the regional capital of Barcelona.

The head of the leftist Catalan nationalist ERC party, Joan Puigcercos, said he would propose a referendum on autonomy for 2011.

"Spain does not like Catalonia. They do not like the way we are, but we submit to their laws," he said.

The head of the centre-right Catalan nationalist CiU party Artur Mas also condemned a ruling that sets "permanent limits" on Catalan self rule.

"Whatever the Constitutional Court says, Catalonia is a nation," he said.

The court struck down 14 of the 233 articles in the charter and changed more than 20 others. But appeals by the PP against more than 80 other points were rejected.

Most significantly, the court ruled that the use of the word "nation" to describe the region had "no legal value" although the court said the article concerned did not violate the constitution.

It accepted one article that makes knowledge of the Catalan language compulsory, but said that a reference to Catalan as the "preferred language" was unconstitutional.

The statute was one of the first initiatives of the Socialist government of Prime Minister Jose Luis Rodriguez Zapatero, which took office in 2004. It was approved by the parliament in Madrid in 2006 and endorsed by Catalan voters in a referendum.

The PP filed a challenge over about half of the articles in the charter before the Constitutional Court in July 2006, arguing that it could lead to the eventual break-up of Spain as a nation.

Catalonia, like other Spanish regions, already controlled most aspects of government, including health and education, before the statute.

The charter gave the regional parliament enhanced powers in taxation and judicial matters as well as more control over airports, ports and immigration.

Many in Catalonia, home to around seven million of Spain's population of some 47 million and which accounts for 25 percent of its gross domestic product, complain that it contributes far more to the Spanish economy than it gets in return.

Monday's court decision could give support to the centre-right nationalists in regional elections scheduled for later this year.

"The reinterpretation of the term 'nation' and the mention eight times of the 'indissoluble unity of Spain' in the ruling will provide plenty of ammunition for rhetoric in the election run-up in Catalonia," said Spain's leading daily El Pais.