I am a project manager in my late 20s. The male colleague in question is late 30s to early 40s I would say. He is a web developer and I oversee the overall projects. My line manager is happy with the way this project is progressing and I have to all in hand.
Well today this developer started saying things 'you need to push the client to get X information because David says the project has to be completed by X date'. David has only said as much because I set that deadline! And I have already done everything he says I 'need' to do.
He has twice today told me he thinks I should set up meetings with my own clients when a meeting has already been set up and it is nothing to do with him. He even asked 'have you done X yet?' about something which is NONE of his business and a line of questioning I expect from my manager only.
Basically I am perfectly capable with what I am doing and am not willing to be undermined in this way. Any tips?