The film is titled They Are Us, a phrase Ms Ardern used in the aftermath of the shootings, which killed 51 people and injured many more.

Acclaimed Kiwi director Andrew Niccol - who directed Gattaca and wrote The Truman Show - is behind the project, with Bridesmaids star Byrne cast as the New Zealand prime minister.

According to a report by US-based entertainment industry news outlet Deadline, the film is being produced in New Zealand, and has been developed in consultation with members of Canterbury's Muslim community.

But the news of the casting and development has angered many in New Zealand, where the grief and trauma from the shooting is still red raw.

"We question the timing and whether a movie is appropriate right now," the Muslim Association of Canterbury's Abdigani Ali said.

"I want to ask if Andrew Niccol and Rose Byrne have read the response of the Royal Commission Inquiry into the attacks?

"Do they know resources of our intelligence agencies had an exclusive focus on a terrorist threat from the Muslim Community?

"We do recognise that the March 15th story will need to be told, but we would want to ensure that it's done in appropriate, authentic, and sensitive matter."

Ms Ardern has distanced herself from the movie, with her spokesman saying "the prime minister and the government have no involvement in the film".

Aliya Danzeisen, Islamic Women's Council of New Zealand national coordinator, expressed her disbelief at the film's production, tweeting "what were they thinking?".

Aya Al-Umari, whose brother Hussein was murdered in the attack, said it was insensitive, tweeting the classic Kiwi-ism "Yeah nah".

"I don't think this film will be received well in New Zealand. My guess is it's Hollywood over-capitalising this," she told AAP.

Auckland-raised journalist Mohamed Hassan said the movie appeared to centre on Ms Ardern at the expense of the impacted community.

"You do not get to tell this story. You do not get to turn this into a White Saviour narrative," he tweeted.

"This pain is still fresh and real. This is upsetting, obscene and grotesque."

Mr Niccol has promised an uplifting movie.

"They Are Us is not so much about the attack but the response to the attack (and) how an unprecedented act of hate was overcome by an outpouring of love and support," he is quoted as saying in the Deadline report.

"The film addresses our common humanity, which is why I think it will speak to people around the world.

"It is an example of how we should respond when there's an attack on our fellow human beings."

Last August, Australian man Brenton Tarrant was sentenced to life imprisonment without parole for carrying out the attack.

Australian Associated Press