On the part of somebody/on somebody’s part
Definition 1 of 3
Pro Tip 1/2Personal Responsibility
Used when assigning blame or responsibility to a specific individual or group. 
The delay was due to an oversight on the part of the project manager.
Pro Tip 2/2Ownership of Actions
Highlights who is responsible for a certain action or outcome, especially in formal contexts. 
This innovation is a remarkable achievement on the part of the research team. 
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