Spain’s new Socialist prime minister is due to meet the hardline nationalist president of Catalonia on Monday amid warnings that Madrid must defend national unity and avoid making any concessions to the separatists who have triggered the country’s most serious political crisis since its return to democracy 40 years ago.

Pedro Sánchez, who took office at the beginning of June after ousting Mariano Rajoy through a no-confidence vote, has shown a more conciliatory approach to the Catalan controversy than his conservative predecessor and has sought to reduce tensions.

Earlier this month, six of the nine Catalan leaders facing charges of sedition, rebellion and misuse of public funds were moved from prisons near Madrid to jails in Catalonia in what was widely seen as a gesture of good faith.

However, while welcoming the talks, the Catalan president, Quim Torra, has made it clear that he will seek a referendum on self-determination. The call will be given short shrift by Spain’s socialist government, which is adamant that the right to self-determination does not exist in the country’s constitution.

Sánchez has instead suggested that parts of the constitution could be reviewed once temperatures have cooled and the powers of Spain’s central and regional governments re-examined.

Inés Arrimadas, the leader of the Catalan branch of the centre-right Ciudadanos party, which won the largest share of the vote in last December’s regional elections, has accused Torra’s government of neglecting and alienating the majority of Catalans who do not support independence.

“What really hurts me most is them portraying all Catalans as pro-independence,” she told the Guardian.

“That’s not true. Right now in Catalonia, there’s a big and very important minority of people who want independence and a majority of Catalans who don’t. But we’re all Catalans and we all deserve respect and a government that respects and defends all of us. But they don’t see that because their thinking is exclusive.”

Arrimadas accused Sánchez of “being mortgaged” to the separatist parties after relying on their support to topple Rajoy, whose People’s party has been embroiled in a series of corruption scandals.

“The PSOE got into government without a plan for government or a parliamentary majority and they’re improvising,” she said. “The only decisions they’ve taken so far are the ones that benefit the nationalists.”

She said existing electoral law needed to be changed as it meant that Catalan separatist parties were over-represented in parliament.

“In Catalonia, the pro-independence parties have 47% of the vote – not even a simple majority – but an absolute majority in seats because of the law that favours them,” she said. “That’s unfair and it’s crazy. In what country would you have a law that gives more power to those who want to break up the country?”

Inés Arrimadas, leader of Ciudadanos in Catalonia, votes in the December election. Photograph: Albert Gea/Reuters

Arrimadas said Sánchez needed to understand that the country required reform, adding: “There can’t be any hang-ups when it comes to defending values such as the equality of the union and the solidarity of Spaniards just as we defend those values in Europe.”

Ciudadanos, which was riding high in the polls before the motion of no-confidence, refused to back Sánchez’s efforts to topple Rajoy. However, Arrimadas rejected suggestions that the party had misjudged the public mood and found itself on the wrong side of history.

“In Spain, no-confidence votes are constructive: it’s not just about showing that you’re rejecting something, it’s also about voting in favour of the alternative,” she said.

“We didn’t want Rajoy’s People’s party … or the alternative that was voted in. We wanted people to have the chance to choose a new, strong government at the ballot box – and one that wouldn’t need the nationalists to govern.”

Arrimadas said last year’s illegal independence referendum and the subsequent unilateral declaration of independence had left Catalan society deeply fractured.

Torra’s government, she said, would do better to stop obsessing over independence and focus instead on issues that affect all Catalans, such as healthcare, employment, infrastructure and the fight against corruption.

Arrimadas also called on the new Catalan president to respect the views of pro-unity Catalans.

“He’s a person who’s written hundreds of xenophobic and supremacist articles. If this gentleman talked about other groups – other races, other religions – the way the talks about Catalans who don’t support independence, he wouldn’t be able to carry on in politics,” she said.

“But because it’s only us he’s talking about, it seems there’s no problem. We’re used to being shamed. But we can’t have a government that humiliates millions of Catalans.”