Spain’s Socialist party leader, Pedro Sánchez, has failed in his first attempt to form a new government after the anti-austerity Unidas Podemos party abstained in a parliamentary vote.

Sánchez, who has been acting prime minister since an inconclusive election in April, needed an absolute majority of at least 176 votes in his favour in the 350-seat house to be confirmed as PM. Instead he received 124 votes in favour and 170 against, and there were 52 abstentions.

The vote now goes to a second round on Thursday when Sánchez only needs a simple majority – ie more “yes” than “no” votes. In the meantime he needs to strike a deal with Podemos in order to secure its MPs’ votes.

Timeline Spain heads for fourth election in four years Show 2015 general election Voter anger over economic woes and corruptions scandals leaders to a hung parliament. The two main parties - the ruling People’s party (PP) and the Socialists (PSOE) - suffer big loses at the expense of newcomers (leftwing) Podemos and (rightwing) Ciudadanos. Neither the PP nor the PSOE manage to secure a majority in parliament to form a new government, so … 2016 General election … another election is held in June. Voter turnout is the lowest since the transition to democracy in 1975. The PP’s vote share increases, but parliamentary deadlock continues. PSOE leader Pedro Sánchez refuses to allow PP leader Mariano Rajoy to form a minority government, citing the corruption scandals swirling around the PP. Sánchez resigns Years of simmering discontent among PSOE members with Sánchez boil over and he is ousted as leader after powerful factions rebel against his refusal to allow Rajoy to form a government. Rajoy secures role as PM With Sánchez gone, the political paralysis is broken and Rajoy returns as PM after the PSOE abstains on an investiture vote in parliament. Sánchez re-elected as PSOE leader Sánchez regains the leadership of the still-divided PSOE, his hardline anti-Rajoy stance bolstered by a slew of corruption scandals involving former senior PP figures in Madrid’s regional government. Rajoy testifies in court Rajoy becomes the first serving Spanish PM to testify in a criminal case. He emphatically denied any knowledge of an illegal funding racket in the PP. Cifuentes scandal The president of Madrid’s regional government, PP's Cristina Cifuentes, resigns after video footage emerged of her apparently being caught stealing two tubs of face cream seven years previously. Rajoy had refused to heed calls to sack Cifuentes after an earlier scandal involving false claims about her academic qualifications. Sánchez becomes PM The PSOE calls a vote of no confidence in the scandal-plagued Rajoy administration, and it passes through parliament with the help of regional parties and Podemos. Sánchez is sworn in as PM the next day. Budget impasse Sánchez is unable to get his 2019 budget passed through parliament after the Basque and Catalan nationalist parties who had supported him against Rajoy vote against it. Yet another election is called. 2019 general election Another inconclusive election sees the PSOE increases its vote share, as the PP vote plummets and the far-right Vox party enters parliament for the first time. Speculation immediately turns to how the PSOE will secure the majority needed to form a government. Fresh elections loom again Sánchez’s efforts to put together a government are hobbled by the refusal of the Citizens party to countenance a pact with the PSOE, and by the socialists’ own firm veto on entering a coalition with Unidas-Podemos. If an agreement is not reached by 23 September a new general election will be held on 10 November.

At the weekend Pablo Iglesias agreed to step aside as Podemos leader after Sánchez accused him of being the main obstacle to forming a coalition. But any hope that Sánchez would respond by offering Podemos senior ministerial positions failed to materialise.

The party was apparently offered the new ministries of youth and housing, as well the vice-presidency for Irene Montero, the Podemos number two and Iglesias’s partner. However, the offer was rejected on the grounds that the posts, which Podemos dismissed as “decorative”, carry no executive power.

“We’re not here to be a Chinese vase,” said party spokeswoman Ione Belarra. “Negotiations are at a standstill but we are confident that the socialist party will reflect and change its position.”

During Monday’s investiture debate an angry Iglesias told Sánchez that the 3.7 million people who voted for his party deserved representation in government.

Montero, who is heavily pregnant, voted no by phone, suggesting that Podemos’s decision to abstain rather than outright oppose was taken at the last minute.

With the support of Podemos’s 42 MPs and a few others from small regional parties, Sánchez could get through on Thursday, but given the anger of these potential allies, that support looks uncertain.

Catalan separatist party ERC accused Sánchez of being “irresponsible” for not appearing to want to negotiate with anyone, while Aitor Esteban of the PNV Basque nationalist party said the Socialists had not even been in touch with them in the past few weeks. “They have taken for granted that our vote was going to be positive,” he said.

Sánchez said on Tuesday: “I invited them [Podemos] to be part of a coalition government, the first in our democracy’s history. I’m trying. I’ve offered to share the cabinet with a parliamentary force that is to the left of the socialist party and which doesn’t guarantee me an absolute majority. You can criticise me for my lack of success in these talks, but not for lack of trying.”

Carmen Calvo, the Socialist party’s vice-president, denied that the posts offered were decorative. “We understand that in negotiations there can’t be winners and losers, that you can agree on some things and not on others,” she said.

If Sánchez cannot secure the votes he needs, he has another two months to find a solution, failing which the Spanish will face another general election.

“What we are seeing in Spanish politics is effectively the natural tensions that occur as a political system transitions from an old way of operating (single-party governments) to what appears to be the new normal … (coalition governments),” Alfonso Velasco, an analyst at the Economist Intelligence Unit, told AFP. “Spain might need another election for politicians to accept the new reality.”

Agence France-Presse contributed to this report