New South Wales Premier Dominic Perrottet has condemned the behaviour of a Liberal Party volunteer, who was sent home from a polling booth after making a racist remark to an Indigenous firefighter.

On Saturday, Liberal volunteers for Camden MP Peter Sidgreaves and Wollondilly MP Nathanial Smith were handing out campaign material at a pre-polling booth on Oxley Street, Camden.

Several professional firefighters were also present, campaigning about under-resourcing.

An Indigenous firefighter — who has asked not to be named — said he was confronted by an older volunteer from the Liberal party who argued firefighters were paid too much.

Later in the day, the firefighter said the volunteer repeatedly used racist slurs against him.

"I told him many others would not be happy with him using that word and that he should stop because someone couldn't be as patient as I am being," the firefighter said.

"I was quite stern at this point as this was the third remark he had made in the matter of minutes."

The slur was overheard by a volunteer supporting Wollondilly independent candidate Judith Hannan, who is contesting the seat for a second time.