Grace Millane was last seen alive on Saturday December 1.

Police have issued a warning to people not to name the man charged with murdering British backpacker Grace Millane on social media.

The reminder comes after the 26-year-old murder accused appeared in the Auckland District Court on Monday, where he was granted interim name suppression.

Following the appearance a number of people took the law into their own hands, naming the man on social media and sharing his Facebook profile.

This prompted Detective Inspector Scott Beard to warn people breaking the suppression order was illegal.

"We would like to remind the public that whilst we appreciate the public feeling around this case, it is an offence to breach a court order such as a name suppression, and this includes naming someone who has name suppression on social media," he said.

Why is the media not reporting his name?

SUPPLIED British tourist Grace Millane, 22, who was killed in Auckland.

At the hearing earlier on Monday, Judge Evangelos Thomas heard arguments from the man's lawyer Ian Brookie on why the accused killer's identity should be kept secret.

Stuff is unable to report the name of the accused on the grounds Brookie advanced, but can say that Millane's father wrote to the judge asking for his daughter's alleged killer to be named.

While Judge Thomas declined Brookie's application - ruling the man should be named - the media were still prohibited from publishing his identity because Brookie issued an immediate appeal.

Abigail Dougherty/Stuff Judge Evangelos Thomas at the hearing on Monday for the accused killer of Grace Millane.

Why was he granted interim name suppression?

Under New Zealand law, a judge who refuses name suppression must grant interim suppression for a 20-day appeal period if the defendant indicates they will appeal.

This means interim name suppression will continue until the appeal on Judge Thomas's decision can be heard in the High Court.

ALDEN WILLIAMS/STUFF Detective Inspector Scott Beard has warned people naming Millane's accused killer is illegal.

The Criminal Procedure Act 2011 lays out the threshold grounds in which a person can be granted interim name suppression.

There are nine grounds in total, which include that publication would "cause extreme hardship to the person charged with, or convicted of, or acquitted of the offence, or any person connected with that person."

Others being that it would "cast suspicion on another person that may cause undue hardship to that person, or cause undue hardship to any victim of the offence, or create a real risk of prejudice to a fair trial."

The Act stipulates that the fact that a defendant is "well known" does not, of itself, mean that publication of his or her name will result in extreme hardship.

Even if the court is satisfied one of the threshold grounds exist it may still exercise its discretion to refuse name suppression.

An interim order is different from permanent name suppression for obvious reasons.

An interim order is only for a limited period of time, while a permanent order may last forever.

Under the Criminal Procedure Act "a court must take into account any views of a victim of the offence" when considering permanent name suppression of a defendant.

It is still unclear when the appeal hearing on name suppression will take place.

What does interim suppression cover?

In this case, the suppression order means no material - text or photos - can be published which would lead to the identity of the accused.

This includes on news websites, but also extends to social media.

Media organisations at the hearing on Monday were allowed to photograph the murder accused but are not able to use those photos until the interim order is discharged.

Publishing the identity of the man could result in prosecution as it is an offence and a contempt of court.

A contempt occurs when a person "wilfully and without lawful excuse disobeys any order or direction of the court in the course of the hearing of any proceedings."