JERUSALEM — A Russian-born billionaire who has become one of Israel’s most colorful public figures promised to stir up politics yesterday by creating his own party.

Arkadi Gaydamak, whose 30-year-old son, Alexandre, owns the Premier League football club Portsmouth, said the Social Justice Party could win as many as 20 seats in the 120-seat Parliament, or Knesset.

While it takes decades for parties to achieve such success in Britain, the use of a pure form of proportional representation in Israeli elections allows for overnight sensations.

The Kadima movement, the leading member of the ruling coalition, became the largest single party in last year’s election only four months after it was founded. With Mr. Gaydamak’s money and flair for publicity, few would bet against his new party.

Speaking at the official launch of Social Justice, Mr. Gaydamak, 55, said his primary ambition was to oust the coalition government led by Prime Minister Olmert, the leader of Kadima.

“There is an urgent need to change the current government that justifies the creation of a party,” he said.

Mr. Gaydamak will serve as party leader and chairman but will not stand for the Knesset himself, preferring to run for the office of mayor of Jerusalem, a key position in Israeli politics.

Messrs. Gaydamak and Olmert have been involved in a highly public clash for several months with the billionaire accusing the prime minister of weak leadership. While some professional politicians have dismissed him as a showman, Mr. Gaydamak has repeatedly shown an ability to connect with the Israeli electorate.

During last summer’s Lebanon war, he was quick to see an opportunity when Mr. Olmert’s government appeared reluctant to evacuate the northern Israeli towns which found themselves within range of rockets fired by Hezbollah.

Mr. Gaydamak personally paid for buses to take the citizens of these towns to safety.

He did the same thing when the southern town of Sderot came under rocket fire from Palestinian Arab militants in the Gaza strip, hiring buses to take the local people on an all-expenses-paid holiday in the Red Sea resort of Eilat. “I am the most popular public figure in Israel,” Mr. Gaydamak said.

“I want to fulfill the wish of the majority of the Israeli population by fundamentally changing things in Israel. I am not aiming to become prime minister, but I wish to play a central role in Israel’s political life.”

Mr. Gaydamak, who owns Beitar Jerusalem, one of the country’s top football teams, and the basketball side, Hapoel Jerusalem, said his party would focus on social issues in a country where poverty has reached alarming levels. Some 1,400 activists have already begun working for Social Justice, which will hold its first meeting in Jerusalem on Thursday.

Although hugely successful as a businessman in Israel, Mr. Gaydamak’s commercial dealings have not escaped critical scrutiny. He is the subject of two French arrest warrants in connection with an arms-dealing case in Angola, forcing Mr. Gaydamak to travel on a diplomatic passport.