Catalonia's President Carles Puigdemont (R) gestures next to Oriol Junqueras, leader of Esquerra Republicana de Catalunya (ERC), during a confidence vote session at Catalan Parliament in Barcelona, Spain September 29, 2016. REUTERS/Albert Gea

MADRID (Reuters) - Catalonia’s parliament voted in favour on Thursday of pursuing a referendum on independence next September amid mounting tensions with Spain’s central government over whether the northeastern region can legally break away.

The referendum poses a new headache for Spain’s acting Prime Minister Mariano Rajoy, whose conservative People’s Party (PP) repeatedly has refused to consider allowing one in Catalonia, which is home to about a sixth of the population.

Rajoy’s stand-off with the Catalan separatists has sharpened at a time when national politics have ground to a halt after two inconclusive national elections over the last 10 months failed to produce a majority to form a central government.

In August, Spain’s central administration asked the Constitutional Court to annul a resolution by Catalonia’s parliament in July to pursue independence. The court on Thursday raised the possibility of bringing criminal charges against the Catalan parliament’s speaker for allowing the vote.

Catalonia’s regional president, Carles Puigdemont, said last Wednesday that he was open to negotiating the terms of a legally binding referendum but he would hold it with or without Spain´s blessing.

Puigdemont comfortably won a parliamentary confidence vote last Thursday in a show of unity that he hoped would spur further support for his independence agenda, which aims to establish basic laws and a state structure by next September.

Some 48 percent of Catalans supported secession in a poll in July, although that it is below its peak from a few years ago.