Under questioning from Labor's Daniel Mookhey Mr Marshall denied he was being cruel to animals when he hit four deer about 10pm March 16 near Emmaville in the state's rural north.

He was briefly investigated by the RSPCA after boasting at the NSW Farmers annual conference in July about his deer-hitting exploits.

"While I'm doing my best in my car to known 'em down four at a time like I did the other night near Emmaville ... the fact is, we need to take some pretty drastic measures to bring that population under control," Mr Marshall said. A video was posted online.

In a Budget Estimates committee hearing on Tuesday he said he wasn't trying to kill them - and only one deer had died.

"I was making light of a serious situation because it was in the context of a discussion about the number of deer being in plague proportions," Mr Marshall said.

"It was in no way an attempt to suggest that I had deliberately run them over. That would be not only ridiculous but also completely inappropriate.

"I was addressing [farmers] who understand exactly what life is like in the bush because that it is what they drive in. Whilst they are unfortunate and are something that people try to avoid, animal strikes are sometimes unavoidable."

The RSPCA made a phone call to Mr Marshall and investigated no more.

He called the investigation "political correctness gone mad". It was actually a shooting advocate who posted the video, wondering what would happen to them if they boasted of the same.