Spain's main left-wing parties agreed after the December 20 elections not to help the country's center-right prime minister to form the next government.

The Socialists, who came second in Sunday's poll with 90 parliamentary seats, have ruled out joining Prime Minister Mariano Rajoy's Popular Party (PP) in a grand coalition. The Popular Party had retained 123 seats in the election but fell far short of the majority needed to govern alone in the 350 seat assembly.

Cesar Luena, one of Socialists' most senior officials, said at a news conference that Spain had voted for change.

"Now it's up to the PP to try and form a government...but the Socialists will vote 'no' to Rajoy and the PP," Luena announced.

Rajoy's future blocked by others as well

In a similar move, the leader of the far-left 'Podemos' movement (which translates as "we can"), said his party - which had won 69 seats - would not support any form of PP alliance.

"On no account will Podemos allow the PP to govern," 37-year-old Pablo Iglesias told reporters.

His anti-austerity movement has helped to dislodge the country's two party politics in its two-year history; a system, which has dominated Spanish politics since the end of the Franco dictatorship in 1975.

Later the leader of Spain's Ciudadanos Party also added that they would not join any coalition and therefore remain in opposition. Ciudadanos (which translates as "citizens") came fourth in the highly fragmented election and is regarded as Rajoy's closest ideological partner.

Despite picking up a strong following in the election, the 40 parliamentary seats garnered by Cuidadanos would not be enough to form a right-wing coalition even if the party changed its mind and were to enter talks with PP.

Voter anger

The announcement by all other parties all but ruled out the possibility of Rajoy forming the next government, after Spanish voters switched allegiance. Voters blamed the PP for its failure to tackle corruption and massive unemployment across the country.

If forced out of government, the PP would become the third political victim in the EU this year of a voter backlash against austerity measures following similar election results in Greece and Portugal earlier in the year.

What next?

Sunday's inconclusive result has raised the fear of political paralysis in Madrid, as a final agreement between parties may take weeks or possibly months to be reached.

Under the Spanish constitution, King Felipe VI will first invite a party leader - normally from the party with the most votes - to form a government. The nominee must receive a majority of votes in parliament in a first round to take office, or the most votes in the second round.

If the candidate is not successful, Parliament has two months to elect a prime minister or call a new election.

mm,ss/jm (AFP, AP, Reuters)