Four jailed Catalan politicians have been suspended as MPs in Spain’s Congress as the country's democracy continues to suffer jolts from an unlawful referendum on independence for Catalonia in 2017.

The speaker of Congress, Meritxell Batet of the Socialist party, explained that Friday’s decision to suspend the Catalan politicians was taken on legal advice because the four are in custody on accusations of rebellion, along with eight other pro-independence leaders also standing trial at Spain’s supreme court.

But the divisive nature of the Catalan issue among Spain’s political forces led to accusations of skulduggery by right-of-centre opposition parties, who accused the ruling Socialists of having tried to avoid suspending the four MPs until after Sunday’s European and Spanish local elections.

The lawmakers, including former Catalan Vice President Oriol Junqueras, for whom prosecutors are seeking a 25 year sentence, were allowed out of prison to swear their oaths of office at Tuesday’s opening of Congress. They promised to obey the Spanish constitution only “out of a legal imperative”, while also swearing loyalty to the Catalan people and what they consider a mandate to secede from Spain.

“The speaker has been making a fool of herself. She was forced to take this decision because the supreme court and her legal advisers said so,” said José Manuel Villegas, parliamentary spokesman for the liberal Ciudadanos party. The Socialist government “humiliate the Spanish people to keep the separatists happy”, Mr Villegas added.