Citizens? Protection Minister Christos Papoutsis has resigned from the government as he intends to challenge for the leadership of PASOK.
The center left party is due to elect a new president to succeed George Papandreou on March 18.
Candidates will have to put their names forward at the party?s national council on March 4.
Finance Minister Evangelos Venizelos is also expected to take part in the contest and is expected to comfortably beat Papoutsis.
Papoutsis came under repeated attack during his time in the Cabinet. He took over from Michalis Chrysochoidis last year and has been criticized for the police?s handling on ant-austerity protests, in particular.