An annual fireworks show "loud enough to shake zombies from their stasis" is sparking outrage among a nearby horsing community.

For the past four years writer Damien Grant has hosted a commercial fireworks display at his Waitoki lifestyle property north of Auckland for his son's birthday - who turns five this weekend.

Last year a row of cars owned by people attending the display were scratched. This year a social media storm is brewing.

"Three wild horses so freshly mustered have just moved in only a few kilometres away ... there is an extremely high chance the fireworks could cause injury or death to these horses," Simone Frewin Kaimanawa, Heritage Horses muster coordinator, said.

Frewin said she had approached Grant about the issue with hope he would see reason but had no such luck.

"I left a message on his phone, he didn't respond, so I emailed him.

"Sadly he is immune to reason and considers the potential enjoyment of the 40 children and more than 80 adults to be of greater importance than serious trauma and potential catastrophic loss of life," Frewin said.

The display was planned for this Saturday night.

Grant said the fireworks would be going ahead and he had every right to do it.

"I sent out a warning notice to all my neighbours within about 4km, giving them plenty of time to move their horses if they were concerned. I've done everything within my legal right."

But Frewin said they couldn't move the horses because they would need a stock cart and they are difficult to get at this time of the year.

"It does raise a bigger issue about commercial-grade fireworks being used for private use and it does need addressing," Frewin said.

Grant said circulating his email and phone number on Facebook was out of line.

"If you react in this way and act like this, then people won't be so considerate to give notice."

The debate took to social media last night triggering bursts of mixed opinions.

Some saying Grant had done everything right, others saying it was inconsiderate.

Frewin, who posted the issue on Kaimanawa Heritage Horses, took the post down this morning, saying it was not her intention to have people abuse or threaten Grant.

"His party is permitted and he's not doing anything illegal. My only intention was to demonstrate just how many people nationwide are concerned about the welfare of NZ's wild horses," Frewin wrote.