Quim Torra, who heads Catalonia's separatist government, on Monday lost his status as a lawmaker in the region's parliament following a disagreement between the chamber's two main pro-independence parties.
It was not immediately clear whether Torra would have to stand down as Catalan president, but the event flagged growing tensions between separatists in this wealthy northeastern region of Spain.
Torra took over as regional president in May 2018 at the head of a coalition made up of Catalonia's two main separatist parties, JxC (Together for Catalonia) and the ERC (Republican Left of Catalonia).
But their time in office has been strained by differences over strategy and loss of support.
In November, Torra went on trial in Barcelona for "disobedience" after refusing to remove separatist symbols from public buildings, and he was convicted last month, with the court banning him from holding public office for 18 months.
Although Torra has appealed the conviction, the electoral commission ordered the Catalan parliament to implement the suspension immediately.
JxC, however, decided to ignore the ruling and asked the ERC to do the same.
But the ERC refused on grounds that ignoring the ruling would render all decisions within the chamber null and void, effectively paralysing the parliament.
Rightwing parties want Torra to step down, and have urged Spain's Socialist Prime Minister Pedro Sanchez to cancel a planned meeting with him in early February.
Sanchez was sworn in for another term on January 8 at the helm of a minority coalition government after very narrowly passing an investiture vote with the support of the ERC. In return, he agreed to open talks with Catalonia's separatist government over the "political conflict".
This latest confrontation between the two Catalan separatist parties has fanned rumours that the region could end up heading to early elections.