By Sarah White and Blanca Rodríguez
MADRID (Reuters) - A leadership bid by Spanish Socialist head Pedro Sanchez looked set to stumble at the first hurdle on Wednesday, as rivals on the left and right ripped into his plans for a coalition at a session of parliament and said they would vote against it.
Spain has made little headway in resolving a political deadlock since a fragmented election result in December, when voters turned in their millions to anti-austerity Podemos ('We Can') and newcomer liberal party Ciudadanos ('Citizens').
An acrimonious debate in parliament on Wednesday, ahead of a vote on Sanchez's plan to team up with Ciudadanos, suggested parties were little closer to putting their differences aside.
Leaders skimmed over policy issues with a volley of recriminations over who was to blame for the deadlock.
"This is a fictitious, unreal candidature," acting Prime Minister Mariano Rajoy of the center-right People's Party (PP) told members of parliament, adding his party would vote against it.
Rajoy branded the alliance, with just 130 seats behind it, as a "bluff" and a threat to national interests which sought only to undo the reforms his government brought in over the past four years.
Sanchez, whose Socialists were runners-up behind the PP in the Dec. 20 ballot, needs an absolute majority -- equivalent to 176 votes -- to be elected prime minister on Wednesday.
His failure would set the clock ticking on a two-month window for parties to try and negotiate a majority in parliament, beyond which a new national election would be called, probably in June.
Even natural allies are still divided on many fronts, at a time when Spain's economic turnaround still needs nurturing, notably to fix a dysfunctional labor market in which unemployment is above 20 percent.
Podemos leader Pablo Iglesias said his party would also vote against Sanchez - spurning his offer of immediate measures to alleviate social inequalities - and push instead for an alliance only between leftist forces.
"Your pact does not protect workers," Iglesias said, accusing Sanchez of aligning with the right.
IN ELECTION MODE
A fraught relationship between Sanchez and Rajoy, meanwhile, has put further distance between the two traditional rivals.
The acting premier's attacks on Wednesday raised questions as to whether he could persuade the Socialists to back him as leader in any subsequent votes in the coming weeks. With 123 seats to its name, the PP is also stuck for allies.
"Rajoy came across as someone already in election mode," said Vincenzo Scarpetta, a political analyst at the Open Europe think tank in London, adding the tense exchanges between leaders had set the scene for a tough two months of talks.
"Based on the debate it has become very difficult to envisage a breakthrough."
An uneven recovery from the economic crisis partly fueled the political backlash in Spain, echoing an upset in Portugal last year that resulted in a fragile leftist coalition. A similar story unfolded in Ireland last week, with an inconclusive election.
Corruption scandals have also tainted mainstream Spanish parties and especially the PP, and these are likely to weigh on negotiations.
Sanchez - who defended his bid to unblock the stalemate after Rajoy passed up the first opportunity to try to form a government - hit back at Rajoy, saying he was becoming "a blockage for the renewal" of his party.
Even Ciudadanos, which praised the PP for helping to reboot the economy, rounded on Rajoy.
"You're not a credible (person) to lead this new political phase," said leader Albert Rivera.
If Sanchez fails in the vote on Wednesday, he would only need to secure the most votes in a second ballot on Friday. But that scenario is unlikely too as the PP and Podemos together command 192 seats.
No candidate for prime minister has failed in both confidence votes since Spain returned to democracy in the mid-1970s.
(Editing by Julien Toyer and Richard Balmforth)