A teenage member of a white nationalist group who failed to assist police investigating a threat to a Christchurch mosque has been fined 500 dollars

Sam Brittenden was arrested in March after he refused to give Police the pass-code to his phone during a search of his home.

The raid was in response to an image circulating on social media - showing a masked man sitting in a car outside the Al Noor mosque - almost a year after the March 15 shootings.

Police eventually accessed the 19-year-old's phone - but no charges were laid in relation to its contents or the threats.

Last year Brittenden, was sentenced to community work and six months' supervision after making anti-Muslim slurs the day after the mosque shootings - while he was studying in Dunedin.