MADRID (Reuters) - Spain’s ruling People’s Party (PP) is more interested in the next election than in cooperating over legislation with its main ally Ciudadanos, and relations between the two have deteriorated, the head of the smaller party said.

Ciudadanos's leader Albert Rivera talks to a reporter during an interview at the Spanish parliament in Madrid, Spain, March 2, 2018. REUTERS/Juan Medina

Ciudadanos has seen its support jump in the polls since a national political crisis erupted over an independence drive in Catalonia, the wealthy northeastern region where the party was formed.

PP Prime Minister Mariano Rajoy’s minority government is relying on it to push through legislation, including delayed budget plans for this year.

But Albert Rivera, leader of the centrist, pro-business Ciudadanos, told Reuters commitments made by the PP when his party agreed to support a second term in office for Rajoy were not being honored.

“Relations have worsened because instead of seeing us as allies they have become obsessed with parliamentary seats and power and they are more scared of losing power in future elections than governing,” Rivera said in an interview in his parliamentary office.

Ciudadanos - “Citizens” in Spanish - came fourth in the last national election in 2016 with 13 percent of the vote.

It backed 62-year-old Rajoy the same year after 10 months of political impasse and two inconclusive elections - contingent on the PP complying with a pact detailing 150 promises from election reform to measures against corruption.

The PP had not kept its side of the bargain, Rivera said, and Ciudadanos would not vote for Rajoy’s long-delayed budget plans for 2018 unless that changed.

“If they don’t keep to the pact, we won’t support them - it’s common sense,” he said.

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Rajoy said in televised comments last month there was no dispute between the PP and Ciudadanos and he was sure Rivera’s party would support the budget.

“LAST THROES”

A deep recession earlier this decade led to voter disengagement with the two parties that have dominated Spanish politics since its transition back to democracy in the late 1970s, giving rise to new political forces.

Formed in 2006 as an antidote to rising separatist sentiment in Catalonia, Ciudadanos went nationwide in 2013.

Its roots stood the party in good stead to capitalize on Spain’s biggest political crisis in decades when Catalonia’s government was sacked by Madrid after it declared independence in October.

Fiercely pro-unity Ciudadanos won the popular vote in December local elections, aimed at putting a new administration in place, although pro-independence parties won most seats. The ruling PP got its worst-ever result in the region.

Since then, Ciudadanos has continued to rise in the polls and some give it the most support nationwide.

Rivera, who aligns himself with liberals like France’s Emmanuel Macron and Canada’s Justin Trudeau, said Spain’s political transition was still under way.

“We’re at the end of the two-party system in Spain,” said the 38-year-old lawyer. “The new has not yet managed to govern and the old has not yet perished or died.”

The separatist movement in Catalonia had weakened, but Ciudadanos’s leader there would not try to form a minority pro-unity government because she would not get enough parliamentary backing, Rivera said.

Late on Thursday, former Catalan leader Carles Puigdemont said he would step aside as presidential candidate for the region after two months of supporters trying to figure out a way to let him lead from self-imposed exile in Brussels.

“I see them agonizing in the last throes of this separatist process,” said Rivera, brought up in a Barcelona suburb by a Catalan father and Andalusian mother, citing a recent poll which saw support for independence dropping to a four-year low.