New Zealand's Justice Minister has warned Google could face prosecution for naming the 26-year-old man accused of murdering British backpacker Grace Millane in a mass email.

Key points: 100,000 Google searches had been made of the man's name nationally

100,000 Google searches had been made of the man's name nationally Google trend alerts are automatically generated based on searches

Google trend alerts are automatically generated based on searches British media widely published the suspect's name, age and personal details

A temporary name suppression order was granted to the suspect while he awaits trial, making it illegal to publish his name in New Zealand.

In a mass email sent to subscribers of Google's "What's trending in New Zealand", the suspect was prominently named in a subhead and following text.

The email said more than 100,000 Google searches had been made of the man's name nationally.

New Zealand website The Spinoff was the first to flag the breach. ( Supplied )

The email was first flagged by popular New Zealand online publication The Spinoff.

A Google spokesperson told the New Zealand Herald they did not know about the suppression order, adding that Google trend alerts were automatically generated based on searches.

Justice Minister Andrew Little told the New Zealand Herald if police traced the breach to Google's New Zealand staff, the firm could be prosecuted.

"They should not be allowed to say 'it's all the machine's problem it's nothing to do with us'," Mr Little said, according to the report.

"The truth is, Google is responsible for publishing in New Zealand information that's been suppressed by a court."

International media also name suspect

A name suppression order can be requested by the accused and victims to protect privacy and ensure a fairer trial for those not yet proven guilty.

If an order is breached, the defence could claim a trial rights violation.

In the Millane murder trial, the suspect's name and personal details — including social media posts and personal photographs — have been widely published online by British media outlets including the Daily Mail, the Evening Standard and the Telegraph.

Photos of Ms Millane were shared on social media after her disappearance. ( Facebook: Saran Millane )

Mr Little made a plea to international media to respect the order, but ultimately it can not be enforced internationally.

"The international media and particularly the British media are not helping the Millane family," Mr Little told reporters in Wellington earlier this week.

"If the British media are concerned about justice and justice for the Millane family they should stop publishing details.

"It will not do justice to the Millane family if the accused in this case gets to walk away from facing justice because somebody has disclosed his details."

The case has raised questions about the effectiveness of suppression orders in the age of the internet.

While the order has been followed by national media, New Zealanders can still view international reports online that name the suspect.

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The man's name and image have also been repeatedly posted and shared on social media.

On Tuesday, police issued a warning to the public via Twitter that posting the suspect's name on social media is an offence.

Ms Millane, 22, was on a year-long world tour after graduating from university.

The British national arrived in New Zealand last month and disappeared from Auckland on December 1. Her body was found by police one week later.

Candlelight vigils have been held around the country.