Spain’s socialist prime minister, Pedro Sánchez, has warned of the dangers of allowing far-right ideology to seep into the political mainstream after the conservative People’s party (PP) struck a series of coalition deals with the radical right Vox party ahead of next month’s general election. Sánchez’s Spanish Socialist Workers’ party (PSOE), which has governed Spain alongside the far-left Unidas Podemos alliance for the past four years, suffered a drubbing in last month’s regional and municipal elections, while the PP made huge gains and Vox doubled its share of the vote. The results, which prompted Sánchez to call a snap general election to be held on 23 July, have given rise to a string of agreements between the PP and Vox to rule the Valencia region and several major Spanish cities in coalitions. While the polls suggest the PP will win next month’s election, it is likely to fall short of an absolute majority and have to rely on Vox’s support to form a government. Sánchez, 51, who is hoping the prospect of a PP-Vox government will serve to galvanise leftwing voters and drive a huge turnout, said the parties’ Valencia deal offered a glimpse of what could lie in store for Spain. “A few months ago, a European leader told me the Spanish election is very important because if things swing towards a PP-Vox government, the balances within Europe will be upset,” the prime minister told El País on Sunday. “There’s something that’s far more dangerous than Vox, and that’s having a PP that assumes the policies and postures of Vox. And that’s what we’re seeing: a denialism when it comes to social, political and scientific consensus. “The fact that the [new] Valencian regional government isn’t mentioning climate change is a denialism that’s dangerous for foreign investment.” Sánchez also pointed to recent, controversial remarks from José María Llanos, Vox’s leader in Valencia, who said “gender-based violence doesn’t exist; violence against women doesn’t exist”. Vox, which dislikes such terms, prefers instead to talk about “intra-family violence”. Llanos’s words were swiftly criticised by the PP leader, Alberto Núñez Feijóo, who is trying to portray his party as moderates even as it forges coalitions with Vox, which named a former bullfighter as Valencia’s regional culture minister earlier this week. “Gender-based violence exists and our society is profoundly shaken every time a woman is murdered,” Feijóo said on Friday. “The PP will never take a step backwards in the fight against this scourge. We will not abandon our principles, whatever the cost.” Llanos later attempted to row back on his comments, saying: “I’d like to clarify and I condemn all violence against women, including by men. But I do deny the existence of gender-based violence.” Sánchez told El País that denying gender-based violence “could only be a step backwards”, adding: “This is what’s at stake on 23 July.” Feijóo, meanwhile, has accused Sánchez of calling the election in a desperate bid to cling to power and criticised him for choosing a date when many Spaniards will be on holiday. If elected, the PP plans to repeal the new Democratic Memory law – which was intended to bring “justice, reparation and dignity” to the victims of the Spanish civil war and subsequent dictatorship – and to scrap recent legislation on trans rights. The party will also re-examine aspects of Spain’s new abortion and euthanasia laws. Following local and regional elections on 28 May, the PP holds absolute majorities in the Madrid region and in the capital’s city council. It has entered coalitions with Vox to govern the cities of Burgos, Ciudad Real, Guadalajara, Toledo and Valladolid, and could use similar pacts to take power in regions including Aragón, the Balearic islands and Extremadura. The municipal elections have also given rise to a new city council in Barcelona after the defeat of Ada Colau, who had served as mayor of the Catalan capital for two consecutive terms. She was unexpectedly succeeded by her Socialist deputy, Jaume Collboni, after the Catalan Socialist party, the PP and Colau’s Barcelona en Comú platform struck a deal that prevented Xavier Trias of the centre-right pro-Catalan independence party Junts per Catalunya (Together for Catalonia) taking office. Trias, who served as mayor of Barcelona from 2011-15, had been expected to become mayor again. But, hours before the parties were due to choose the new leader of the city council, Barcelona en Comú announced it would back Collboni in order to avoid a Junts administration that would “roll out red carpets for lobbies and sectors favourable to rightwing policies”.