MADRID (Reuters) - The leader of Ciudadanos, the third-biggest group in parliament after Spain's election, said on Tuesday the party will not form a coalition with the winning Socialists but intends to play a responsible role in opposition.
With Prime Minister Pedro Sanchez's centre-left Socialist Party seeking allies after Sunday's vote that left it short of a parliamentary majority, the centre-right Ciudadanos, which won 57 seats in the 350-seat assembly, had already ruled out a partnership.
Such a deal would be welcomed by many in business and financial circles. Ciudadanos leader Albert Rivera reiterated there would be no coalition, while promising not to block major international or terrorism-related legislation.
"On issues of terrorism, on issues of Europe and international politics, on state issues, I am going to play for Spain," he told Telecinco television.
Ciudadanos' seat total is up from 32 in the previous legislature and Rivera is jockeying with the conservative People's Party leader Pablo Casado, over who will be leader of the opposition. The PP won 66 seats, less than half what it had before.
Speaking after a weekly cabinet meeting, Isabel Celaa, a spokeswoman for the outgoing government, welcomed Rivera's remarks but noted that tensions had been high between the Socialists and Ciudadanos.
"If Rivera wishes to be more reasonable, well that's very welcome," Celaa told reporters.
The Socialists are pondering options on how to form a government, something that is not likely to be resolved before EU, local and regional elections on May 26.
"We, the Socialists, are open to talks with everyone ... to explore any (potential) agreements. We have time" before the local elections, Celaa said.
The Socialists increased their seats to 123 from 84 in the previous parliament, meaning that if they joined forces with Ciudadanos they would have enough seats to form a government.
But until now both parties have rejected a coalition and relations between Rivera and Sanchez were particularly tense during the campaign.
Jose Luis Abalos, a high-ranking Socialist, said on Monday that Rivera had not phoned Sanchez to congratulate him on his victory. Ciudadanos said later that Rivera had congratulated Sanchez publicly in a Sunday evening speech and had sent him a message on Monday.
(Reporting by Sabela Ojea; Additional reporting by Belen Carreno; Writing by Ingrid Melander and Andrei Khalip; Editing by Frances Kerry)