Madrid, May 27 (IANS/EFE): Defence Minister Carme Chacon said Thursday she is stepping down from the Spanish government to seek the ruling Socialist party's nomination for prime minister in the March 2012 general elections.

The incumbent premier, Jose Luis Rodriguez Zapatero, announced last month that he would not be seeking a third four-year term.

Chacon told a hastily arranged press conference she decided to formally launch her campaign now after the Socialists suffered a worse-than-expected battering in Sunday's regional and municipal elections.

"I think I must take a step back for the PSOE (Socialist Workers Party of Spain) to take a step forward," she said, adding that "many members" had urged her to seek the prime ministerial nomination.

The recent triumph at the polls of the main opposition conservative Popular Party ignited a fierce debate within the PSOE about the succession to Zapatero.

One potential rival to Chacon is Deputy Prime Minister Alfredo Perez Rubalcaba, a PSOE warhorse whose national career began in the early 1980s during the tenure of then prime minister Felipe Gonzalez.

For her to remain part of the current administration while vying to succeed Zapatero as party standard-bearer could undermine party unity and even "the stability of the government", Chacon said Thursday.

The PSOE president of the Basque region, Patxi Lopez, said in the wake of Sunday's electoral debacle that the party should consider forgoing planned internal primaries and instead convene a general assembly to address issues beyond the succession to Zapatero.