The family of a March 15 terror attack victim has written to Hollywood star Rose Byrne asking her to refuse the role in a proposed new movie, saying it is too soon.

Early plans for a new film, They Are Us, which would focus on the response by Prime Minister Jacinda Ardern were revealed last week and met with outrage and horror by many of the victims' families and the wider New Zealand Muslim community.

A petition launched on Friday night seeking to have the project cancelled has already been signed by more than 40,000 people.

It says the movie sidelines the victims and survivors and instead centres on the response of a white woman, while calling on the funders, producers and the New Zealand film industry to boycott the film, and urges Ardern to publicly denounce it.

The Prime Minister released a statement on Friday saying that film-makers did not consult her in any form about their plans.

Christchurch Mayor Lianne Dalziel also slammed the idea and said film crews would not be welcome in The Garden City.

Now, the family of Linda Armstrong, who was shot dead at the Linwood Islamic Centre on March 15, 2019, by an Australian terrorist, has written directly to one of the film's proposed stars.

Byrne has reportedly been slated to play Ardern – who was widely praised for her response to the shooting attacks on two city mosques that claimed the lives of 51 people.

But Kyron Gosse, Armstrong's nephew, has written on behalf of his family to reach out to star actor Byrne to turn down the role, saying the family needs time to heal.

"Now is not the time, and this is not the story," Gosse writes.

"Please, turn down the role and give us time to heal."

Gosse contacted the Herald to say he was "appalled" by the movie.

"Linda Armstrong was my aunt and she was one of the victims at the Linwood Mosque," he said.

"As such I have written an open letter to Rose Byrne requesting her not to take the role."

The full open letter to Rose Byrne:

Dear Rose, I urge you to rethink your role as Jacinda Ardern in the movie They are Us. We know that a movie being made about what happened on that dreadful day is inevitable, however for now it is too soon. It was only 27 months ago that our country was thrown into shock and turmoil. It was only 27 months ago that I had to google my aunt's name to see if she was alive or dead. It was only 27 months ago that I stood in her grave, lowering her lifeless body into the ground. Please, give us time. It was only 15 months ago that the one-year remembrance was cancelled by the onset of Covid. It was only 15 months ago that our family was forced to flee back home as borders shut, destroying our healing process. It was only 15 months ago that the terrorist pleaded guilty. Please give us time. It was only nine months ago that I stood face to face with the terrorist in the Christchurch High Court to deliver my victim impact statement. It was only seven months ago that the Royal Commission's report was released detailing that the terrorist's intentions should have been picked up by our intelligence agencies. It was only two months ago that the gunman requested a court appearance to challenge his designation as a terrorist. This story is far from over and for the families involved, we still live it every single day. Please, give us time. Two years is far too soon to be talking about Hollywood movies. In contrast: It took 85 years to release the Titanic movie. It took 16 years to release a 9/11 movie. It took six years to release the Deepwater Horizon movie. The time will come for this story to be told. When the right time does arrive, it is important that the right story is told, a story that focuses on the true heroes of the day. Now is not the time, and this is not the story. Please, turn down the role and give us time to heal. Yours faithfully, Kyron Gosse (on behalf of the Gosse family).