Existing multimodal representation learning approaches often rely on simple feature concatenation or unified transformations, which fail to effectively disentangle and leverage common and private information across different modalities in a progressive manner. Moreover, they typically lack adaptive modeling tailored to specific task requirements. To address these limitations, we propose a Prototype-Induced Label Structuring for Disentangled Multimodal Representation Network (PLUM-Net). It first employs a multilevel semantic alignment module to synchronize global and local semantics across audio, visual and textual streams. On this aligned foundation, a prototype-based single-modal label generation module derives modality-specific hard and soft-labels that subtly steer the network toward a cleaner split between shared and private cues. Guided by these labels, the task-conditioned feature bifurcator module channels information through the most beneficial common or private pathway for the given task, after which a private refinement module polishes and fusion each modality’s idiosyncratic signals. Extensive experiments show that PLUM-Net delivers strong performance on datasets such as CMU-MOSI, CMU-MOSEI and UR-FUNNY, achieving an ACC-2 of 90.3% on CMU-MOSI and 83.2% on UR-FUNNY .