A meeting of UML's parliamentary party elected him to the post and also promoted lawmaker Bhanu Bhakta Dhakal as the ruling party's chief whip.
The post for deputy leader remained vacant ever since the election while the position for the chief whip went vacant after erstwhile Agni Kharel was made minister for law and justice.
Prime Minister KP Sharma Oli was elected party's parliamentary party leader defeating former party chief Jhalanath Khanal in a voting among the party's lawmakers.
Nembang was earlier promoted to the post of the party's standing committee member after he retired as speaker in October.
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