A "crude and offensive" text asking a gang member's partner for sex was answered - but not with the sort of attention the sender was seeking.

Sean Verma's partner went to look at a property advertised for rent on July 25. The man who showed her around texted her later in the day saying it had been let to someone else. He also asked her for oral sex.

Verma texted back, posing as his partner, and arranged to meet the man. He smashed his car windows with a bat, demanded his keys, and told the man he was dealing with the Mongrel Mob.

The man, whose name is suppressed, managed to drive away, escaping with just superficial cuts to his face.

Verma, 29, of Petone, sent more texts telling the man he was "dead", saying he knew what his business was, and with references to the man's parents and property he owned. The man apologised and asked how he could make things right.

He offered to pay $5000 the next day - but Verma demanded $10,000.

Had he settled for $5000, Verma might have got away with it, Justice Miller told him in the High Court at Wellington yesterday.

Instead, he was sentenced to home detention after earlier pleading guilty to blackmail, assault and wilful damage.

Justice Miller said Verma had been "significantly provoked" by the crude sexual advance. The man admitted he had been out of line and that the events would not have happened but for his own behaviour.

Verma was sentenced to 10 months' home detention and ordered to pay $1300 for damage to the car. He has been made redundant from his job at New Zealand Post and is to pay the reparation at $10 a week from a welfare benefit.

The judge said that, despite Verma's gang affiliation and age, he had only a minor list of previous convictions.

The sentence will separate Verma from his family, who have to move out of the flat because the judge said the constant presence of a person on home detention could stress a household.