Keum Tae-sup, a former lawmaker, defected from the ruling Democratic Party (DP) on Wednesday, denouncing what he called its arrogance, hypocrisy and partisan antagonism.

He has been at odds with mainstream members over a raft of issues including prosecution reform and a scandal involving a former justice minister. He was disciplined in May for refusing to follow the party line in a crucial parliamentary vote.

"I came to a state where I cannot approve of or agree with the direction the DP is heading toward," he wrote on his Facebook post, announcing his departure from the party.

He lambasted what he called the party's arrogant attitude with which it has pitted the people against each other and attacked rivals as criminals or pro-Japanese collaborators.

"The party is infinitely lenient toward allies but harsh on rivals, flipping positions on issues with a brazen face," he said.

The former DP spokesperson also slammed the party's culture of self-righteousness in which "healthy criticism and self-reflection are condemned as shooting at allies."

Keum was among only a few members of the DP who openly criticized former Justice Minister Cho Kuk late last year over a scandal surrounding his daughter's academic records and family's dubious investment.

In December, the renegade politician rejected the party's policy to support a bill on the establishment of a new investigative body in charge of corruption involving high-ranking officials.

Amid widespread internal backlash, he lost a party primary ahead of the April parliamentary elections.

In May, the former legislator received a warning from the party ethics committee for refusing the party line vote. He immediately appealed, but the panel has yet to consider his request.

Keum, now a lawyer, told Yonhap that he will not retire from politics.

"I will continue to work as a politician," he said, without elaborating on his future course of action.

It has been speculated that he will run in the election for Seoul mayor as an independent or representing an opposition party. (Yonhap)