Spain’s coalition government has vowed to overturn an “authoritarian” initiative by the far-right Vox party that allows parents to stop their children attending talks, workshops or classes during school hours whose content “goes against their moral principles”.

According to Vox, the policy – referred to as the “parental pin” – is designed to protect children by requiring parental permission for exposure to content relating to “ethical or social values or civic or sexual morals”.

But critics claim it will shut down debate on gender, sexual orientation, feminism and the environment as the scheme also requires parental consent for any activity relating to “socially controversial moral questions or sexuality”.

Although the initiative featured in Vox’s manifesto for last April’s general election, and has been in effect since last September in the south-eastern region of Murcia – where Vox props up a regional government between the conservative People’s party (PP) and the centre-right Citizens party – it has only recently become a topic of fierce debate.

Last week, Vox threatened to veto the Murcia government’s annual budget unless the PP and Citizens adopted the parental pin as part of the regional education programme.

Although the pin was not signed into law, the regional budget was agreed after a deal was reached to allow “families to educate their children freely, without any kind of impositions, through the express permission of families when it comes to their children’s participation” in extracurricular classes and activities.

The debate could have more national consequences as Vox has also played kingmaker to PP-Citizens coalition regional governments in Madrid and Andalucía.

The new central government of the Spanish Socialist Workers’ party (PSOE) and the far-left, anti-austerity Unidas Podemos alliance, said last week that it would work to have the scheme overturned – by legal means if necessary – as it “goes against constitutional values”.

Spain’s new equalities minister, Irene Montero, described the measure as an attempt at educational censorship.

“The sons and daughters of homophobic parents have the same right as everyone else to be educated about respect, the promotion of human rights and being able to love whoever they want,” she said last week.

“The sons and daughters of sexist parents also have the same right to be educated about equality and feminism.”

On Monday, eight regional education ministers from the PSOE published an open letter decrying the parental pin as a measure that would “rupture school harmony and the culture of dialogue and reflection and impose a blind and uncritical authoritarianism”.

Pablo Casado, leader of the PP, said a balance needed to be found between freedom of choice and information for parents, adding that he thought most “sensible” Spaniards wanted to decide what kind of education their children receive.

“I don’t believe in a country where parents have to be subject to the whims of what a politician or bureaucrat says,” Casado said on Monday.

He also renewed his attack on the new government’s decision to appoint a former justice minister, Dolores Delgado, as the new attorney general, saying the outrage over the parental pin was a “smokescreen” to distract from criticisms of the move.

Critics argue that Delgado’s appointment blurs the separation of powers, with some members of the General Council of the Judiciary suggesting it could serve to “create the appearance of a link with the executive branch that does not contribute to the perception of the judiciary’s independence”.