SEOUL (AFP) - South Korea' faction-riven opposition was in total disarray on Tuesday (Jan 19) after leader Moon Jae In said he was resigning ahead of a predicted rout in April parliamentary elections.

Citing internal opposition to his efforts to reform the party, Mr Moon said he would step down as soon as an interim party leadership could be put in place.

"I was unable to achieve party unity and in order to do so, I've decided to step down to facilitate party solidarity," he said.

The opposition's losing presidential candidate in 2012, Mr Moon has come under mounting pressure to take responsibility for splits within the opposition camp and the departure of several high-profile figures.

The most recent - and most damaging - defection was of Mr Ahn Cheol Soo, a popular one-time IT tycoon and party co-chairman, who left to form his own political group, taking dozens of other members with him.

Mr Ahn accused Moon of playing factional politics and surrounding himself with loyalists.

The opposition's implosion has left President Park Geun Hye's ruling Saenuri Party rubbing its hands with glee at the prospect of a landslide victory in the upcoming election.

Even before the opposition's latest setback, opinion polls suggested Ms Park's party could secure more than 60 per cent of parliamentary seats.