Israeli Defence Minister Ehud Barak broke away from his centre-left Labour Party on Monday in a move Prime Minister Benjamin Netanyahu said made his government stronger and more stable.
Barak will remain as defence chief in the right-leaning government, while the three remaining Labour ministers quit the cabinet, bringing the once-dominant political party that pioneered peace efforts with the Palestinians into opposition.
The split removes the risk that a left-wing rival could have replaced Barak as Labour leader and pulled the whole party out of the ruling coalition, possibly bringing the government down.
The government has grown much stronger today, in its governance, in its stability -- and this is important for Israel, Netanyahu told reporters.
The whole world knows and the Palestinians know that this government will be around for the next few years and that it is with this government that they should negotiate for peace.
Labour's presence in the coalition had broadened the government's political base and softened its right-wing image abroad at a time when its policy of settlement-building on land Palestinians want for a state has led to a peace talks freeze.
The split could further marginalise Labour, which dominated Israel for most of its history but saw its support erode in the past decade with the failure of the peace process pioneered in the 1990s under Labour leaders Yitzhak Rabin and Shimon Peres.
Barak served as Labour's last prime minister from 1999-2001, but was voted out after failing to finalise a peace deal with the Palestinians. His decision to join Netanyahu's right-wing government had alienated many core Labour supporters.
At a news conference announcing he and four of Labour's 13 legislators would form a new Atzmaut (Independence) faction, Barak said he had faced a never-ending fight watching Labour's continuous drift to the left and again to the left.
In a letter to the Labour Party, Barak's deputy Matan Vilnai, who defected with him, said the split would enable the government to pursue peace without a stopwatch.
An official close to Netanyahu said the prime minister had no plans to increase the number of ministers in the cabinet, although it was quite likely that members of Atzmaut would be the ones to replace the Labour ministers who had quit.
HUMP ON ITS BACK
Labour stalwarts see leaving Netanyahu's government as a step towards restoring the movement's stature.
The Labour Party, which founded the state of Israel and its institutions, rid itself today of a hump on its back, said Welfare Minister Isaac Herzog, one of the ministers to quit.
Tzipi Livni, head of the main opposition Kadima party, said Barak's redrawing of Israel's political map meant that today the camp opposing Netanyahu grew, and it will keep growing until Netanyahu falls.
Binyamin Ben-Eliezer, who held the trade and industry portfolio, seemed best placed to succeed Barak as Labour chief.
The split left the government, which controlled 74 seats in the 120-member parliament, with 66 votes, usually a comfortable governing margin in Israel.
Ultimately, this move is going to serve to stabilise the government and in so doing we hope to strengthen the peace process, said a member of Netanyahu's staff.
There were people who were telling the Palestinian leadership that the Labour Party was about to bolt, that the coalition is unstable, that they can wait this government out, added the staff member, who asked not to be identified.
Direct peace negotiations with the Palestinians that began under U.S. sponsorship in September quickly froze after Netanyahu refused to extend a partial moratorium on new housing in Jewish settlements in the occupied West Bank.
Nabil Abu Rdainah, a spokesman for Palestinian President Mahmoud Abbas, called Barak's move an internal Israeli matter.
What matters to us is the presence of an Israeli government and Israeli parties committed to the peace process, he said.