The "New Politics Alliance for Democracy" officially launched Wednesday afternoon in a ceremony at Olympic Stadium in Seoul.
The new party will be co-headed by former Democratic Party leader Kim Han-gil and Ahn Cheol-soo of the New Political Vision Party.
Kim and Ahn will jointly lead the party for one year until it elects a party chairman and leadership next year.
The alliance adopted its platforms at the ceremony based on four main pillars: forming a just society, achieving social integration, creating a prosperous economy, and maintaining peace in the country.
In an apparent move to garner more support ahead of the upcoming June elections,.. the platforms show neutral policy orientations that aim to appeal more to the country's middle class voters.
The alliance means the new united opposition party will have 130 seats at the National Assembly.
The ruling Saenuri Party currently has 156 seats in the parliament.
Saenuri representatives are criticizing the launch of the new party, saying it's merely a move to pursue short-term political gains, not to serve the livelihoods of the people.
Political insiders say more challenges lie ahead for the new party, such as resolving conflicts between the former leader of the Democratic Party and the New Political Vision Party.
Kim Han-gil and Ahn Cheol-soo announced their plans to form the new party earlier this month, with an ultimate goal of achieving a transfer of power in the presidential elections in 2017.
Connie Kim, Arirang News.