The Spanish lawyer Miriam González Durántez has launched a new liberal, centrist party, vowing to clean up politics and give voters an alternative to the dominant socialist and conservative parties as the country gears up for next month’s snap general election.

González Durántez, an ex-EU adviser who is married to the former British deputy prime minister Nick Clegg, says her new party, Democracia21, will offer a modern, transparent kind of politics that “doesn’t feed on fear, insults or nostalgia”.

Democracia21’s manifesto accuses both the ruling Spanish Socialist Workers’ party (PSOE) and the rightwing People’s party (PP) of squandering decades of government for short-term political ends.

“In the meantime: housing became unaffordable, young people left, bureaucracy grew like a religion, and bickering took the place of governing,” it says. “Old-school politics turned every problem into a narrative – and every solution into an electoral threat.”Mindful of the corruption scandals that eventually toppled the last PP government – and the graft allegations enveloping the administration and inner circle of the socialist prime minister, Pedro Sánchez – the new party is promising “a radical political cleanup”, including far greater transparency for parties.

González Durántez, who announced that Democracia21 will run in Madrid and Barcelona in the election on 29 November, has also positioned herself on two of the biggest issues facing voters: the housing crisis and immigration.

The eviction last month of an 87-year-old woman in Madrid unleashed waves of demonstrations across Spain, led to the setting up of a protest camp in the centre of the capital and prompted Sánchez’s minority government to propose emergency measures to try to make the rental market more equitable. When those measures were voted down by rightwing and far-right parties at the beginning of October, the prime minister announced a snap general election.

Speaking at her party’s launch over the weekend, González Durántez accused both the PSOE and the PP of ignoring the housing crisis.

“One lot has been in government for eight years and the other controls 80% of Spain’s regional governments,” she said. “What’s going on here is that they only remember about housing when an election comes around and all the people are on the streets.”González Durántez proposed scrapping housing taxes for people under 35, and argued that a young person earning €1,300 (£1,098) a month should not be paying more than €350 a month in rent.

She also defended the benefits of controlled immigration and of Spain’s place within the European project, which she described as “absolutely existential” for the country.

“Immigration is an asset and an essential competitive advantage for Spain right now,” she said. “We need to get rid of all the xenophobic talk but the state needs to be in control of immigration. We need to decide who comes in; how they come in; when they come in and, if they have to leave, we will also decide when they leave. None of this is contradictory. We need to do all that while ensuring that Europe doesn’t fall into the traps of those political forces that haven’t come to reform Europe, but to break it.”

Democracia21 is not the first centrist party to have tried to shake up the traditional socialist and conservative duopoly. The liberal Ciudadanos party, founded in 2006, briefly looked set to push past both the PSOE and the PP, but its decision to lurch to the right and its refusal to back the no-confidence motion that turfed the conservatives out of office in 2018 proved fatal. Ciudadanos’s support was so depleted by the last general election in July 2023 that it chose not to take part in the poll.

Sánchez’s decision to call the snap election is another gamble from Spain’s pragmatic and unpredictable prime minister. Polls suggest the PP will comfortably beat the PSOE to win first place, but is unlikely to secure an absolute majority, forcing it to rely on Vox’s support to govern.

Sánchez, meanwhile, will be hoping that the PP’s decision to side with Vox and the rightwing Catalan pro-independence Junts party to torpedo the housing proposals will mobilise leftwing and moderate voters.

The prime minister, however, is already facing an electoral setback after Spain’s supreme court decided to maintain its suspension of the voting rights of tens of thousands of overseas voters who benefited from a law his government introduced in 2022 offering Spanish citizenship to the descendants of those exiled during the civil war and subsequent Franco dictatorship.

The move has angered the PP and Vox, who have accused Sánchez of seeking to create more socialist voters beyond Spain’s borders. Although the suspension looks set to remain in place for the election, the court has said its ruling will not affect those who can prove that their parents or grandparents “suffered exile for political or ideological reasons, or for reasons of belief or sexual orientation”.

The PSOE has denounced the political pressure behind the decision as an affront to democracy.

“The grandchildren of the Franco regime will be able to vote, but not those of the exiles, just as the PP and Vox wanted,” the party’s organisational secretary, Rebeca Torró, posted on X. “Their fascist agenda has struck at the cornerstone of democracy: the right to vote. We will not stop denouncing this outrage.”