Greece's citizens' protection minister, Christos Papoutsis, resigned on Monday to run for the leadership of the socialist PASOK party headed by former prime minister George Papandreou.
Papandreou, who stepped down as prime minister in November last year to make way for a new coalition government and help Greece resolve its biggest financial crisis in decades, has said that he intends to step down as socialist party leader as well.
"In a letter sent to Prime Minister Lucas Papademos, minister Papoutsis submitted his resignation from the government in order to become a candidate for president of PASOK," his ministry said in a statement.
PASOK, which is due to elect a leader next month, is struggling in opinion polls after two years of austerity policies and trails the conservative New Democracy party ahead of elections expected in April.
The two parties form the coalition government headed by Papademos, a technocrat, but are expected to be punished by voters for backing a bailout package that includes painful wage and spending cuts.
Pollsters say the PASOK leadership battle could determine whether the socialists rebound in opinion polls. Finance Minister Evangelos Venizelos is expected to be the frontrunner to take over as party leader.