Is this a phase? How do I deal with it?

[TheGrandOldDuke]

hi all,
My son is 2.5yrs. In the last two weeks he has discovered a shouty growl that is just horrible. If you ask him to do something he shoutgrowls "I need my mummy/daddy" ( whichever one isn't there) and refuses to do whatever is asked.
Nursery have said he is doing this there, complete with a shouted 'no!' when asked to do something. I don't know where he's got it from, so am hoping it's a phase they all go through. They also said at nursery he is pushing a bit more and being rougher in play.
95%of the time he is just lovely to be around.
Is it best to ignore this? Or naughty step him each time? I don't know whether reacting to it gives him attention if that is what he is doing it for, and perhaps therefore it's better just to walk away from him?
Any ideas anyone??
Thanks!

Personally, I would be ignoring it. But then I never did naughty step.

Does it push your buttons when he does it? I.e. does he get a reaction, any reaction? Because if so, then that could be a reason.

If you are able to stay very calm and simply repeat the instruction, that could work too. But I found that harder, so would frequently end up walking away.

No it doesn't really wind me up, I just think it's horrible and rude. He's done it twice during bath time so I've ignored him and just got him out the bath without eye contact.
I really try to praise the good behaviour and he gets huge amounts of attention from me, but I guess they always want more?!