In a tweet, Joaquim Forn said he had “taken the decision” to head up “a unifying, reliable and transversal” electoral list in Barcelona for municipal polls on May 26.
The announcement comes as a trial against him and 11 other pro-independence leaders begins shortly over a failed attempt to separate the northeastern region of Catalonia from the rest of Spain in October 2017.
At the time, Forn was in charge of interior matters in the pro-independence executive of former regional president Carles Puigdemont, who fled Spain for Belgium.
Members of the deposed Catalan regional government (L-R) Joaquim Forn, Raul Romeva, Jordi Turull, Carles Mundo, Josep Rull and Meritxell Borras arrive at the National Court in Madrid on November 2, 2017.
Prosecutors want Forn to be jailed for 16 years for rebellion and misuse of public funds.
A councillor in Barcelona's city hall for 18 years, Forn will head up the list of Puigdemont's separatist party PDeCAT in the municipal elections.
He pres la decisió d'encapçalar una candidatura integradora, solvent i transversal per guanyar l'alcaldia de Barcelona. Vull liderar un projecte de transformació de la ciutat sòlid i rigorós per situar Barcelona, de nou, al centre de tot.
Llegiu la meva carta oberta: pic.twitter.com/aAPMjR450O
— Joaquim Forn (@quimforn) January 23, 2019
His main rivals will be Ada Colau, the current left-wing mayor of Spain's second biggest city, former French prime minister Manuel Valls who was born in Barcelona and Ernest Maragall for the separatist ERC party.
Maragall is the brother of Barcelona's ex-Socialist mayor Pasqual Maragall, still popular for his role in the city's successful bid for the 1992 Olympics.
In his statement, Forn said being in jail would not be a problem.”I can't accept that just because I am locked up I cannot set in motion the transformation project I have for Barcelona,” he said.
This is not a first in Catalonia.
In snap regional elections in December 2017, Catalonia's former vice president Oriol Junqueras was an ERC candidate and campaigned from jail via various writings and speeches read by colleagues.
He won a seat in the regional parliament as did other jailed separatists.
Junqueras will also stand for European elections due on May 26, the same day as the municipal polls.