Stavros Theodorakis, the leader of centrist To Potami, announced his intention to resign from the party's leadership, during a meeting of its political council on Tuesday.
Potami fared badly in Sunday's EU elections, receiving just 1.51 percent of the vote – much lower than the 3 percent threshold required to enter parliament.
In the 2014 elections, the party had secured 6.62 percent, sending two MEP to Brussels.
During the meeting, he proposed Giorgos Mavrotas as his successor. He also said he will not run again for the Greek Parliament with Potami or any other party.
Theodorakis, who founded Potami in February 2014, also suggested that the party does not run in the upcoming national elections but added he will reserve his final opinion until all party officials have expressed their view.