Speaking at a press conference in Tel Aviv, Barak slammed Prime Minister Netanyahu and unveiled his new political movement, calling it a response to the prime minister's recent move to consider the canceling of the September 17 elections he himself had led the nation to.
"All Israeli citizens need to remember who was behind these elections," said Barak, adding that it was only "the grave circumstances" that led him to the decision.
"The future of the Zionist movement is on the line here," Barak said, and called upon Netanyahu to resign of his own accord before it is too late.
"As your former commander, I tell you, Netanyahu, you cannot continue … your time as a political leader is over," said Barak.
Barak served as the IDF's 14th chief of staff from 1991 to 1995. He initially entered the private sector after leaving the army, but soon after embarked on a political career in Labor, taking over the leadership after Shimon Peres' 1996 electoral defeat and beating incumbent Benjamin Netanyahu in the 1999 Knesset elections to become prime minister.
Barak served in office until 2001, when he was defeated by Likud leader Ariel Sharon in a special election for the prime ministership of the country following the outbreak of the Second Intifada.
In 2007 he was appointed defense minister by then-prime minister Ehud Olmert, and in 2012 announced his retirement from politics.
Earlier this week, it was reported that former deputy chief of staff Yair Golan is working with Barak to establish the party. Golan spoke in the press conference and slammed the repeating attacks on the Israeli left.
Former Air Force pilot and chair of the Darkenu political movement Kobi Richter and Yifat Bitton, number two in Gesher Party are also expected to join the new party.
Earlier this month, reports claimed that former foreign minister Tzipi Livni was under pressure to join the new party. Livni announced February that she was retiring from politics.