NSW Rural Fire Service Commissioner Shane Fitzsimmons says Prime Minister Scott Morrison did not inform him he was deploying 3000 army reservists to help with the bushfire crisis and the timing of the announcement hampered the response effort on a catastrophic day.

Commissioner Fitzsimmons said it was "disappointing" to hear about the announcement via media reports amid a horror day for the state, adding it had tied up resources.

"All I can say is I wasn't aware of it, I found out about it via the media reports," Commissioner Fitzsimmons told Nine's Today show.

"We then spent a fair bit of time with the military liaison and the Commonwealth liaison that are embedded here in our centre trying to understand what the details were."